All SAT Critical Reading Resources
Example Questions
Example Question #2 : Analyzing Argumentative Claims, Bias, And Support In Natural Science Passages
Adapted from “Introduced Species That Have Become Pests” in Our Vanishing Wild Life, Its Extermination and Protection by William Temple Hornaday (1913)
The man who successfully transplants or "introduces" into a new habitat any persistent species of living thing assumes a very grave responsibility. Every introduced species is doubtful gravel until panned out. The enormous losses that have been inflicted upon the world through the perpetuation of follies with wild vertebrates and insects would, if added together, be enough to purchase a principality. The most aggravating feature of these follies in transplantation is that never yet have they been made severely punishable. We are just as careless and easygoing on this point as we were about the government of the Yellowstone Park in the days when Howell and other poachers destroyed our first national bison herd, and when caught red-handed—as Howell was, skinning seven Park bison cows—could not be punished for it, because there was no penalty prescribed by any law. Today, there is a way in which any revengeful person could inflict enormous damage on the entire South, at no cost to himself, involve those states in enormous losses and the expenditure of vast sums of money, yet go absolutely unpunished!
The gypsy moth is a case in point. This winged calamity was imported at Maiden, Massachusetts, near Boston, by a French entomologist, Mr. Leopold Trouvelot, in 1868 or 69. History records the fact that the man of science did not purposely set free the pest. He was endeavoring with live specimens to find a moth that would produce a cocoon of commercial value to America, and a sudden gust of wind blew out of his study, through an open window, his living and breeding specimens of the gypsy moth. The moth itself is not bad to look at, but its larvae is a great, overgrown brute with an appetite like a hog. Immediately Mr. Trouvelot sought to recover his specimens, and when he failed to find them all, like a man of real honor, he notified the State authorities of the accident. Every effort was made to recover all the specimens, but enough escaped to produce progeny that soon became a scourge to the trees of Massachusetts. The method of the big, nasty-looking mottled-brown caterpillar was very simple. It devoured the entire foliage of every tree that grew in its sphere of influence.
The gypsy moth spread with alarming rapidity and persistence. In course of time, the state authorities of Massachusetts were forced to begin a relentless war upon it, by poisonous sprays and by fire. It was awful! Up to this date (1912) the New England states and the United States Government service have expended in fighting this pest about $7,680,000!
The spread of this pest has been retarded, but the gypsy moth never will be wholly stamped out. Today it exists in Rhode Island, Connecticut, and New Hampshire, and it is due to reach New York at an early date. It is steadily spreading in three directions from Boston, its original point of departure, and when it strikes the State of New York, we, too, will begin to pay dearly for the Trouvelot experiment.
How does the author feel about Howell?
The author thinks that Howell made a great mistake in releasing Gypsy moths into the United States.
The author likes Howell because he helped identify a problem with the consequences available for environmental disruptors.
The author greatly dislikes Howell for his audacious disrespect for nature.
The author is annoyed by Howell’s insistence that invasive species do not cause significant problems.
The author agrees with Howell that invasive species are often problematic.
The author greatly dislikes Howell for his audacious disrespect for nature.
Let’s look at the part of the first paragraph in which the author brings up Howell, paying attention to why he does so:
“The most aggravating feature of these follies in transplantation is that never yet have they been made severely punishable. We are just as careless and easygoing on this point as we were about the government of the Yellowstone Park in the days when Howell and other poachers destroyed our first national bison herd, and when caught red-handed—as Howell was, skinning seven Park bison cows—could not be punished for it, because there was no penalty prescribed by any law.”
In mentioning Howell, the author is providing an example supporting his argument that harsher legal penalties are necessary for those who harm the environment. The author describes Howell as a “poacher” who “destroyed our first national bison herd” and was “caught red-handed.” From this, we can tell that the best answer choice is “the author greatly dislikes Howell for his audacious disrespect for nature.”
One of the other answer choices attempts to get you to confuse Howell with Mr. Trouvelot, who released the gypsy moths—don’t fall for that! Check the passage if you are worried at all about confusing the two so you can avoid pitfall answers like that one.
Example Question #3 : Analyzing Argumentative Claims, Bias, And Support In Natural Science Passages
Adapted from “Introduced Species That Have Become Pests” in Our Vanishing Wild Life, Its Extermination and Protection by William Temple Hornaday (1913)
The man who successfully transplants or "introduces" into a new habitat any persistent species of living thing assumes a very grave responsibility. Every introduced species is doubtful gravel until panned out. The enormous losses that have been inflicted upon the world through the perpetuation of follies with wild vertebrates and insects would, if added together, be enough to purchase a principality. The most aggravating feature of these follies in transplantation is that never yet have they been made severely punishable. We are just as careless and easygoing on this point as we were about the government of the Yellowstone Park in the days when Howell and other poachers destroyed our first national bison herd, and when caught red-handed—as Howell was, skinning seven Park bison cows—could not be punished for it, because there was no penalty prescribed by any law. Today, there is a way in which any revengeful person could inflict enormous damage on the entire South, at no cost to himself, involve those states in enormous losses and the expenditure of vast sums of money, yet go absolutely unpunished!
The gypsy moth is a case in point. This winged calamity was imported at Maiden, Massachusetts, near Boston, by a French entomologist, Mr. Leopold Trouvelot, in 1868 or 69. History records the fact that the man of science did not purposely set free the pest. He was endeavoring with live specimens to find a moth that would produce a cocoon of commercial value to America, and a sudden gust of wind blew out of his study, through an open window, his living and breeding specimens of the gypsy moth. The moth itself is not bad to look at, but its larvae is a great, overgrown brute with an appetite like a hog. Immediately Mr. Trouvelot sought to recover his specimens, and when he failed to find them all, like a man of real honor, he notified the State authorities of the accident. Every effort was made to recover all the specimens, but enough escaped to produce progeny that soon became a scourge to the trees of Massachusetts. The method of the big, nasty-looking mottled-brown caterpillar was very simple. It devoured the entire foliage of every tree that grew in its sphere of influence.
The gypsy moth spread with alarming rapidity and persistence. In course of time, the state authorities of Massachusetts were forced to begin a relentless war upon it, by poisonous sprays and by fire. It was awful! Up to this date (1912) the New England states and the United States Government service have expended in fighting this pest about $7,680,000!
The spread of this pest has been retarded, but the gypsy moth never will be wholly stamped out. Today it exists in Rhode Island, Connecticut, and New Hampshire, and it is due to reach New York at an early date. It is steadily spreading in three directions from Boston, its original point of departure, and when it strikes the State of New York, we, too, will begin to pay dearly for the Trouvelot experiment.
Which of the following best describes an opinion held by the author?
Despite spending a great deal of money, the United States will never be rid of the gypsy moth.
Efforts to contain the gypsy moth will improve as technology improves, until all of the moths in the United States have been eradicated.
It is difficult to say what the future holds for the fate of the gypsy moth in the United States.
We should introduce a new species of animal that eats gypsy moths to combat the problems they cause.
Farmers should place nets around their fields and orchards to prevent the gypsy moths from getting to their crops.
Despite spending a great deal of money, the United States will never be rid of the gypsy moth.
The first sentence of the passage’s last paragraph provides the information we need to answer this question correctly: the author writes, “The spread of this pest has been retarded, but the gypsy moth never will be wholly stamped out.” We can thus definitively say that he thinks that “despite spending a great deal of money, the United States will never be rid of the gypsy moth.”
Example Question #2 : Analyzing Argumentative Claims, Bias, And Support In Natural Science Passages
"The Multiple Sides of Computer Science" by Matthew Minerd (2014)
It often takes some time for a new discipline to become recognized as an independent science. An excellent example of this is computer science. In many ways, this science still is a hodgepodge of several different sciences, each one having its own distinct character. For example, some computer scientists are almost indistinguishable from mathematicians. Many of the most difficult topics in pattern recognition and data communications require intensive mathematics in order to provide software solutions. Years of training in the appropriate disciplines are necessary before the computer scientist can even begin to work as a programmer in such areas. In contrast to those computer scientists who work with complex mathematics, many computer scientists work on areas of hardware development that are similar to disciplines like electrical engineering and physics.
However, computer science has its own particular problems regarding the unity of its subject matter. There are many practical applications for computing work; therefore, many computer scientists focus on learning a large set of skills in programming languages, development environments, and even information technology. All of these disciplines have a certain practical coloration that is quite distinct from the theoretical concepts used in other parts of the field. Nevertheless, these practical topics add to the broad range of topics covered by most academic programs that claim to focus on “computer science.” It can only be hoped that these disciplines will increase in orderliness in the coming decades.
Which of the following would strengthen the author’s main contention?
None of these
Even social sciences like behavioral psychology are often studied in order to help develop artificial intelligence algorithms.
Almost all computer scientists have some ability in a major programming language.
All computer science departments require calculus.
No computer science curricula include studies from biology and chemistry.
Even social sciences like behavioral psychology are often studied in order to help develop artificial intelligence algorithms.
The general point of the passage is that it is hard to find the "focus" of computer science. A number of the answers actually help to find the focus—either (1) by stating what all (or almost all) study or (2) by excluding certain subjects entirely (chemistry / biology); however, if computer scientists also studied behavioral psychology it would be yet one more topic in the "mix" of many different subjects studied.
Example Question #4 : Analyzing Argumentative Claims, Bias, And Support In Natural Science Passages
Adapted from "Taking a Second Look: An Analysis of Genetic Markers in Species Relatedness" by Joseph Ritchie (2014)
Phylogenetics is the study of genetic composition in various species and is used by evolutionary biologists to investigate similarities in the molecular sequences of proteins in varying organisms. The amino acid sequences that build proteins are used to construct mathematical matrices that aid in determining evolutionary ties through the investigation of percentage similarities. The study of these matrices helps to expose evolutionary relationships between species that may not have the same overt characteristics.
Species adapt and evolve based on the pressures that exist in their environment. Climate, food source, and habitat availability are only a few factors that act on species adaptation. These stressors can alter the physical characteristics of organisms. This divergence in evolution has made it difficult to determine the interrelatedness of organisms by analyzing their physical characteristics alone.
For instance, looking only at physical characteristics, the ghost bat resembles a pigeon more than a spider monkey; however, phylogenetics has found that the amino acid sequences that construct the beta hemoglobin molecules of bats are twenty percent more similar to those of mammalian primates than those of birds. This helps reject the assumption that common physical characteristics between species are all that is needed to determine relatedness.
The differences produced by divergent evolution observed in the forest-dwelling, arboreal spider monkey and the nocturnal, airborne ghost bat can be reconciled through homology. Homologous characteristics are anatomical traits that are similar in two or more different species. For instance, the bone structure of a spider monkey’s wrist and fingers greatly resembles that of a bat’s wing or even a whale’s fin. These similarities are reinforced by phylogenetic evidence that supports the idea that physically dissimilar species can be evolutionarily related through anatomical and genetic similarities.
Paragraph four of the passage discusses which of the following?
the physiological functions of the spider monkey’s wrist and fingers, the bat’s wing, and the whale’s fin.
the reasons why a spider monkey’s wrist and fingers can resemble a bat's wing or a whale's fin.
the unreliability of physical characteristics in determining species relatedness.
the theory of evolution.
the reasons why a spider monkey’s wrist and fingers can resemble a bat's wing or a whale's fin.
One of paragraph four's central purposes is to give examples of homologous adaptation. It describes how the features of different species can possess anatomical similarities, even if the species are from vastly different habitats. The passage does not discuss the theory of evolution nor the physiological purposes of certain appendages, and the third paragraph, not the fourth, discusses the unreliability of physical characteristics in determining species relatedness.
Example Question #3 : Science Passages
"The Multiple Sides of Computer Science" by Matthew Minerd (2014)
It often takes some time for a new discipline to become recognized as an independent science. An excellent example of this is computer science. In many ways, this science still is a hodgepodge of several different sciences, each one having its own distinct character. For example, some computer scientists are almost indistinguishable from mathematicians. Many of the most difficult topics in pattern recognition and data communications require intensive mathematics in order to provide software solutions. Years of training in the appropriate disciplines are necessary before the computer scientist can even begin to work as a programmer in such areas. In contrast to those computer scientists who work with complex mathematics, many computer scientists work on areas of hardware development that are similar to disciplines like electrical engineering and physics.
However, computer science has its own particular problems regarding the unity of its subject matter. There are many practical applications for computing work; therefore, many computer scientists focus on learning a large set of skills in programming languages, development environments, and even information technology. All of these disciplines have a certain practical coloration that is quite distinct from the theoretical concepts used in other parts of the field. Nevertheless, these practical topics add to the broad range of topics covered by most academic programs that claim to focus on “computer science.” It can only be hoped that these disciplines will increase in orderliness in the coming decades.
What will be the effect of increased orderliness in computer science studies?
It will set to rest the debates about computer science's importance
It will make scheduling much easier for most students
It will help to overcome biases against practical applications of computer science
It will be easier to understand the distinct topic studied in computer science
It will allow for greater progress in experimentation
It will be easier to understand the distinct topic studied in computer science
The main focus of this whole passage is the fact that it is hard to figure out the single thing studied by computer science. It has many branches, all of which seem to be rather different and unrelated (or at least not very related). With increased orderliness, we can assume that it will become clearer just what is the special topic studied in computer science—as opposed to mathematics, physics, or information technology.
Example Question #292 : Isee Middle Level (Grades 7 8) Reading Comprehension
"Darwinism's Effect on Science" by Matthew Minerd (2014)
For much of the history of human thought, the sciences have studied subjects that seemed to be eternal and unchanging. Even the basic laws of the Nile’s flooding were investigated in the hopes of finding never-altering laws. Similarly, the scientific investigations of the ancient Near East and Greece into the regular laws of the stars ultimately looked for constant patterns. This overall pattern of scientific reasoning has left deep marks on the minds of almost all thinkers and found its apotheosis in modern physics. From the time of the early renaissance to the nineteenth century, physics represented the ultimate expression of scientific investigation for almost all thinkers. Its static laws appeared to be the unchanging principles of all motion and life on earth. By the nineteenth century, it had appeared that only a few details had to be “cleared up” before all science was basically known.
In many ways, this situation changed dramatically with the arrival of Darwinism. It would change even more dramatically in early twentieth-century physics as well. Darwin’s theories of evolution challenged many aspects of the “static” worldview. Even those who did not believe that a divine being created an unchanging world were shaken by the new vistas opened up to science by his studies. It had been a long-accepted inheritance of Western culture to believe that the species of living organisms were unchanging in nature. Though there might be many different kinds of creatures, the kinds themselves were not believed to change. The thesis of a universal morphing of types shattered this cosmology, replacing the old world-view with a totally new one. Among the things that had to change in light of Darwin’s work was the very view of science held by most people.
Consider the underlined sentence. What was the new “cosmology” that arose after Darwin’s day?
A completely areligious outlook on life.
The belief that history was an important but secondary aspect of scientific studies.
None of the other answers
The view of the world as an unchanging whole to be investigated by science.
The view of the world as a changing reality with its own historical nature.
The view of the world as a changing reality with its own historical nature.
Throughout the second paragraph, the passage discusses again the "static" nature of the former scientific outlook. The new worldview was quite different. You can guess at the meaning of "cosmology" by noticing the contrast between it and "universal morphing of types." A "cosmology" is a particular outlook on the world or reality as a whole. The passage implies that Darwin's work made it necessary to see the world as a changing whole with its own history.
Example Question #1 : Analyzing Cause And Effect In Natural Science Passages
"Interpreting the Copernican Revolution" by Matthew Minerd (2014)
The expressions of one discipline can often alter the way that other subjects understand themselves. Among such cases are numbered the investigations of Nicolaus Copernicus. Copernicus is best known for his views concerning heliocentrism, a view which eventually obliterated many aspects of the ancient/medieval worldview, at least from the standpoint of physical science. It had always been the natural view of mankind that the earth stood at the center of the universe, a fixed point in reference to the rest of the visible bodies. The sun, stars, and planets all rotated around the earth.
With time, this viewpoint became one of the major reference points for modern life. It provided a provocative image that was used—and often abused—by many people for various purposes. For those who wished to weaken the control of religion on mankind, it was said that the heliocentric outlook proved man’s insignificance. In contrast with earlier geocentrism, heliocentrism was said to show that man is not the center of the universe. He is merely one small being in the midst of a large cosmos. However, others wished to use the “Copernican Revolution” in a very different manner. These thinkers wanted to show that there was another “recentering” that had to happen. Once upon a time, we talked about the world. Now, however, it was necessary to talk of man as the central reference point. Just as the solar system was “centered” on the sun, so too should the sciences be centered on the human person.
However, both of these approaches are fraught with problems. Those who wished to undermine the religious mindset rather misunderstood the former outlook on the solar system. The earlier geocentric mindset did not believe that the earth was the most important body in the heavens. Instead, many ancient and medieval thinkers believed that the highest “sphere” above the earth was the most important being in the physical universe. Likewise, the so-called “Copernican Revolution” in physics was different from the one applied to the human person. Copernicus’ revolution showed that the human point of view was not the center, whereas the later forms of “Copernican revolution” wished to show just the opposite.
Of course, there are many complexities in the history of such important changes in scientific outlook. Nevertheless, it is fascinating to see the wide-reaching effects of such discoveries, even when they have numerous, ambiguous effects.
What can we say of the effects of Copernicus’ discoveries on the reigning medieval way of looking at the world?
It only effected the ideas concerning the human person in comparison with the vast universe.
It questioned every received authority with detailed critiques.
It had little effect in the final analysis.
It required significant changes in its natural science and its manner of considering the human person.
It completely discredited everything from the Middle Ages.
It required significant changes in its natural science and its manner of considering the human person.
Clearly, the theories of Copernicus had significant effects on the medieval mindset. Although the passage does not indicate that it required complete revision on every point, it does imply that it had an effect both on the medieval conception of the human person as well as its scientific conceptions of the world.
Example Question #115 : Psat Critical Reading
Adapted from An Introduction to Astronomy by Forest Ray Moulton (1916 ed.)
It is doubtful if any important scientific idea ever sprang suddenly into the mind of a single man. The great intellectual movements in the world have had long periods of preparation, and often many men were groping for the same truth, without exactly seizing it, before it was fully comprehended.
The foundation on which all science rests is the principle that the universe is orderly, and that all phenomena succeed one another in harmony with invariable laws. Consequently, science was impossible until the truth of this principle was perceived, at least as applied to a limited part of nature.
The phenomena of ordinary observation, as, for example, the weather, depend on such a multitude of factors that it was not easy for men in their primitive state to discover that they occur in harmony with fixed laws. This was the age of superstition, when nature was supposed to be controlled by a great number of capricious gods whose favor could be won by childish ceremonies. Enormous experience was required to dispel such errors and to convince men that the universe is one vast organization whose changes take place in conformity with laws which they can in no way alter.
The actual dawn of science was in prehistoric times, probably in the civilizations that flourished in the valleys of the Nile and the Euphrates. In the very earliest records of these people that have come down to modern times it is found that they were acquainted with many astronomical phenomena and had coherent ideas with respect to the motions of the sun, moon, planets, and stars. It is perfectly clear from their writings that it was from their observations of the heavenly bodies that they first obtained the idea that the universe is not a chaos. Day and night were seen to succeed each other regularly, the moon was found to pass through its phases systematically, the seasons followed one another in order, and in fact the more conspicuous celestial phenomena were observed to occur in an orderly sequence. It is to the glory of astronomy that it first led men to the conclusion that law reigns in the universe.
What does this passage imply to be the effect of not understanding the causes of events?
It was caused by mythology, which distracted people from reality.
It is one of the greatest sources of ill in societal development.
It was only overcome by overthrowing all religion in favor of scientific reasoning.
It led to mythological beliefs in other supernatural causes.
None of the other answers
It led to mythological beliefs in other supernatural causes.
In the passage, the author discusses the fact that sometimes cause and effect relationships are difficult to elaborate, particularly when many causes come together to make an effect occur. This often causes people to attribute such complex events to the gods. Although mythology might encourage people to remain ignorant, the passage does not really state that.
Example Question #201 : Passage Based Questions
"Comparing Technologies: A Difficult Endeavor" by Matthew Minerd (2014)
Comparisons of technology are often difficult to make, not only because of the rapid pace of improvements but also because of the many new applications that are available as time progresses. If we were to consider the contemporary graphing calculator and the calculation capacities of computing machines from fifty years ago, there would be astounding improvements between these two devices. However, the improvements are not reduced merely to speed improvements. A graphing calculator also has numerous output capacities that far exceed those available much older computers, none of which had the ability to represent their output in any manner even closely resembling that of contemporary devices. Merely consider the display capacities of such a device. These enable users to input many new kinds of information, enabling design engineers to design new hardware functions to match the new means of collecting user input.
The situation is even more obvious when one considers the numerous functions performed by a modern “smartphone.” These devices are equipped with a panoply of features. With all of these new functions come many new types of computational capabilities as well. In order to process images quickly, specialized hardware must be designed and software written for it in order to ensure that there are few issues with the phone’s operation. Indeed, the whole “real time” nature of telecommunications has exerted numerous pressures on the designers of computing devices. Layers of complexity, at all levels of production and development, are required to ensure that the phone can function in a synchronous manner. Gone are the days of asynchronous processing, when the computer user entered data into a mainframe, only to wait for a period of time before the processing results were provided. Today, even the smallest of digital devices must provide seamless service for users. The effects of this requirement are almost beyond number.
What is the effect of the features found on modern “smartphones”?
They require increased memory capacities to accommodate their advancements.
They wear out old equipment, requiring newer, faster processors.
None of the other answers
They overwhelm the customer with options all on one screen.
They require many new types of technological advancements to accommodate them.
They require many new types of technological advancements to accommodate them.
Although the whole of the second paragraph helps to answer this question, a key sentence is, "With all of these new functions come many new types of computational capabilities as well." The effect of the new capabilities is to require many different kinds of new capabilities for the software and hardware of phones. That is, many new technological advances are required in order to make them possible and more efficient.
Example Question #13 : New Sat Reading
Adapted from The Effects of Cross & Self-Fertilisation in the Vegetable Kingdom by Charles Darwin (1876)
As it is impossible to exclude such minute pollen-carrying insects as Thrips, flowers which it was intended to fertilise with their own pollen may sometimes have been afterwards crossed with pollen brought by these insects from another flower on the same plant; but as we shall hereafter see, a cross of this kind does not produce any effect, or at most only a slight one. When two or more plants were placed near one another under the same net, as was often done, there is some real though not great danger of the flowers which were believed to be self-fertilised being afterwards crossed with pollen brought by Thrips from a distinct plant. I have said that the danger is not great because I have often found that plants which are self-sterile, unless aided by insects, remained sterile when several plants of the same species were placed under the same net. If, however, the flowers which had been presumably self-fertilised by me were in any case afterwards crossed by Thrips with pollen brought from a distinct plant, crossed seedlings would have been included amongst the self-fertilised; but it should be especially observed that this occurrence would tend to diminish and not to increase any superiority in average height, fertility, etc., of the crossed over the self-fertilised plants.
As the flowers which were crossed were never castrated, it is probable or even almost certain that I sometimes failed to cross-fertilise them effectually, and that they were afterwards spontaneously self-fertilised. This would have been most likely to occur with dichogamous species, for without much care it is not easy to perceive whether their stigmas are ready to be fertilised when the anthers open. But in all cases, as the flowers were protected from wind, rain, and the access of insects, any pollen placed by me on the stigmatic surface whilst it was immature, would generally have remained there until the stigma was mature; and the flowers would then have been crossed as was intended. Nevertheless, it is highly probable that self-fertilised seedlings have sometimes by this means got included amongst the crossed seedlings. The effect would be, as in the former case, not to exaggerate but to diminish any average superiority of the crossed over the self-fertilised plants.
Errors arising from the two causes just named, and from others,—such as some of the seeds not having been thoroughly ripened, though care was taken to avoid this error—the sickness or unperceived injury of any of the plants,—will have been to a large extent eliminated, in those cases in which many crossed and self-fertilised plants were measured and an average struck. Some of these causes of error will also have been eliminated by the seeds having been allowed to germinate on bare damp sand, and being planted in pairs; for it is not likely that ill-matured and well-matured, or diseased and healthy seeds, would germinate at exactly the same time. The same result will have been gained in the several cases in which only a few of the tallest, finest, and healthiest plants on each side of the pots were measured.
Kolreuter and Gartner have proved that with some plants several, even as many as from fifty to sixty, pollen-grains are necessary for the fertilisation of all the ovules in the ovarium. Naudin also found in the case of Mirabilis that if only one or two of its very large pollen-grains were placed on the stigma, the plants raised from such seeds were dwarfed. I was therefore careful to give an amply sufficient supply of pollen, and generally covered the stigma with it; but I did not take any special pains to place exactly the same amount on the stigmas of the self-fertilised and crossed flowers. After having acted in this manner during two seasons, I remembered that Gartner thought, though without any direct evidence, that an excess of pollen was perhaps injurious. It was therefore necessary to ascertain whether the fertility of the flowers was affected by applying a rather small and an extremely large quantity of pollen to the stigma. Accordingly a very small mass of pollen-grains was placed on one side of the large stigma in sixty-four flowers of Ipomoea purpurea, and a great mass of pollen over the whole surface of the stigma in sixty-four other flowers. In order to vary the experiment, half the flowers of both lots were on plants produced from self-fertilised seeds, and the other half on plants from crossed seeds. The sixty-four flowers with an excess of pollen yielded sixty-one capsules; and excluding four capsules, each of which contained only a single poor seed, the remainder contained on an average 5.07 seeds per capsule. The sixty-four flowers with only a little pollen placed on one side of the stigma yielded sixty-three capsules, and excluding one from the same cause as before, the remainder contained on an average 5.129 seeds. So that the flowers fertilised with little pollen yielded rather more capsules and seeds than did those fertilised with an excess; but the difference is too slight to be of any significance. On the other hand, the seeds produced by the flowers with an excess of pollen were a little heavier of the two; for 170 of them weighed 79.67 grains, whilst 170 seeds from the flowers with very little pollen weighed 79.20 grains. Both lots of seeds having been placed on damp sand presented no difference in their rate of germination. We may therefore conclude that my experiments were not affected by any slight difference in the amount of pollen used; a sufficiency having been employed in all cases.
Based on the passage, a purpose for the damp sand was to __________.
eliminate errors which occur during germination
allow healthy seeds to avoid diseased ones
ward off insects such as Thrips
give the author the ability to see the pairs of seeds during germination
allow thorough drainage for the seedlings
eliminate errors which occur during germination
In the third paragraph, the line “Some of these causes of error will also have been eliminated by the seeds having been allowed to germinate on bare damp sand” suggests that one potential purpose of using bare damp sand instead of soil was to protect against some of the errors which could have otherwise occurred.