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The record of it should include an accurate statement of the conditions at the beginning of the experiment, together with drawings of the apparatus and material as the experiment is set up. In other words, aim to make your notes usable in the future. Set this test-tube aside to cool for a moment or two. Into a test-tube one-fourth full of clear water place 3 or 4 drops of iodine solution, using a pipette. Shake the mixture and describe the resulting color. Pour one-half of this mixture into another test-tube one-half full of water. OCCURRENCE OF CARBOHYDRATES IN PLANTS 47 starch test, as above outlined. Be careful to distinguish between your observations and your inferences. The process of con- verting starch into sugar is termed hydrolysis, and since it converts an insoluble substance into a soluble one, it is a kind of digestion. The sugar ordinarily used for culinary purposes is cane sugar. Explain how cane sugar differs from starch chemically. — To demonstrate a test for the presence of grape sugar (C6H12O6). The reagent commonly used for this test is called Fehling's solution, from the name of the scientist who first employed it. (i) 17.5 grams of copper sulphate dissolved in 500 c.c. (2) 86.5 grams of sodium-potassium- tartrate (Ro- chelle salts) in 500 c.c. It is better to make this test even with fresh solution. Place a very small amount of grape sugar into a test- tube one-third full of water. Shake the solution and gently warm it, then add a few drops of Fehling's solution. (5) Also imbedded in the parenchyma, and sur- rounding the iimer sclerenchyma, several areas of fibro-vascular bundles.

Next follows the observation, which must always be made and recorded at the time and place of the experi- ment. Fin- ally, there may be stated the inference, that is, the A LABORATORY GUIDE FOR GENERAL BOTANY conclusion or conclusions which are thought to be justi Jied by the facts observed. Your text-book may be regarded in one sense, as the author's laboratory note-book. Drawing is one of the greatest aids to observation. It is often said that "persons who cannot draw cannot see." This is probably an extreme statement, but it is undoubtedly true that one who can make an accurate drawing of a thing has observed it more accurately than one who cannot. Laboratory drawings should aim to represent the thing only as it is, not as it may impress one at first sight. The solution is prepared by mixing one volume of each of the following stock solutions with two volumes of distilled water (e.g., 10 c.c. In fresh specmiens these areas are yello^\"ish, in preserved material they are lighter colored POLYPODIUM VULGARE J I than the inner sclerenchyma. Comparison of Gametophyte and Sporophyte of Poly- podium: Copy the following table into your note-book, and mark X after the word gametophyte or sporophyte in the proper column. QJ 1 M 1 03 1 1 m S Ah S CO '0 u pi U (U J a'2 a ^ "o X ^ W43 to 3 " n, •" 2 pq ft *" S m ft Has bot tive an ductive Gametophyte Sporophyte Polytrichum commime (Common hair-cap moss)V A.

The scientific method is not peculiar to the natural sciences : it is just as essential in history or language-study as elsewhere, and the highest success in any intellectual pursuit is not possible if the requirements of the scientific method are dis- regarded. If so, record that fact, and endeavor to ascertain TO THE STUDENT Z whether your specimen is abnormal, or whether your observation of it is at fault in any way. In mere observation one takes conditions as he finds them; in experimentation, he determines, within limits, the conditions under which the observation is made. ^'The greatest thing a human being ever does in this world, ^^ said John Ruskin, "i^ to see something, and tell what he saw in a plain way.'^ 9. (d) Observe the end of a rhizome, cut squarely across. Do you find any outgrowth from the tip of any of the archegonial plants? Are the moss-plants differentiated into root and shoot?

Always try to see all you can with the unaided eye before resorting to the aid of a hand lens or microscope. It is never possible to control, absolutely, all the conditions in any experiment, but this is partly compensated for by arranging side by side of the experiment proper, a check or control. Secondly, the note-book serves as an index, to the instructor, of what you have done and how well you have done it. Mount a few threads of cotton (cotton wool) in water under a cover glass. Irrigate under the cover glass Ts-ith a Kttle dilute sulphuric acid, and follow the acid ^"ith the iodine solution. If preserved material is used, the cut surface should be kept moistened during the study.

It should be used only after one has seen all that he possibly can with the unaided eye. The following points should be constantly borne in mind : (a) Keep all parts of the instrument, especially the lenses, scrupulously clean. (e) Never touch the lens with the fingers or eyelids. If notj state reasons for considering some of them younger than others. What structure is the starting point of the sporo- phyte? Diagram the life history of the fern for three genera- tions, by continuing the following diagram; letting G = gametophyte; s = sperm ;e = egg; S = sporo- phyte ; sp = asexual spore : GS-?

(/) Never try to clean the lens with the handkerchief or anything except lens paper, {g) Never examine any object without covering it with a cover-glass. Find e\-idence in your specimen of the method of formation of the pinnae. {£) Describe and compare the venation of the blade, and of the indi\idual pinnae.

Dirt will be magnified as well as the object you are studying. ^lake a careful drawing of a portion of the cross-section, including one complete bundle and at least a quarter of each bundle on each side; this will be a V-shaped sector with the point at the center of the stem-section and the arc at the periphery. From another petiole cut off a portion at least 15 cm. Record the exact length of the piece in millimeters. With a scalpel carefully remove a thin strip of outer tissue along the entire length of the piece (or remove a strip of ''bark" from a very young woody stem). Record this measure, and calculate the percentage of change in length. From another portion of the petiole cut off two strips from opposite sides (or the bark from a portion of some young woody stem). From the preceding studies describe the condition of the tissues in a plant stem. Compare the fern leaf in this respect with the foliage-leaf of a seed-bearing plant. Compare several specimens with reference to this point. Nearer the notch observe the archegonia, appearing, in cross-section, to be composed of four cells, sur- rounding an opening or canal. By the side of this figure draw an out- line of the prothallus, natural size. In fresh specimens motile antherizoids or sperms may be found escaping from the antheridia and swimming in the water. Describe accurately, noting the differentiation of the archegonium into a neck, containing a neck-canal, and a venter, containing an oosphere or egg. Make a diagram of the section, of the same scale as the drawing in 3 above, and make drawings showing details of structure of the antheridia and archegonia as seen in longitudinal section. To what class of reproductive bodies do the sperm and egg of the fern belong?

(/) Handle all slides and cover-glasses by the edge, never touching their surface with the fingers. Radiating from the center and between each pair of bundles are the medullary rays. Into what tissue do they merge toward the periphery? (c) and (d) In boiling water for two or three min- utes. Obtain a petiole of rhubarb, or burdock, or a stalk of celery. Describe the position assumed by the severed piece. Place one of the excised strips in water, another in a 10 per cent, salt solution. At the end of five or ten minutes compare the lengths of the two strips, {a) with each other, {h) with the portion of the stem from which they were cut. (i) Describe the appearance of very young, unex- panded leaves or portions of leaves. Is their position constant {j.e., always the same) ? (w) Observe, using hand lens if necessary, that the sorus is composed of a group of small organs (sporangia). ^ POLYPODIUM VULGARE 73 (n) Is there a membranous expansion (indusimn) covering the sporangia in your specimen? Among the rhizoids find small elevations, the antheridia. If these are found, observe the body -of the sperm and the cilia. To which of the alter- nating generations does the prothallus belong?

The latter is merely an aid to the eyes, but not to the mind, and is made necessary by the limited range of our unaided vision. If it is ever absolutely necessary to do so, then {d) Never lay a lens down on the table. in diameter, and with the scalpel make a dean cut lengthwise through the bark, and remove the bark, being careful not to crack or break it. At once, or at the end of four or me minutes, try to replace the bark. (/) Do the pinnae appear to be all of the same age? Make a diagram to show the life cycle of the fern, using arrows and words, arranged in a circle. Brooklyn Botanic Garden, CONTENTS Page To the Student i PART I ANATOMY AND PHYSIOLOGY Meaning of the Terms 9 A Generalized Plant {Spirogyra) ii A Specialized Plant (e.g., The Bean Seedling) i6 Structure of the Foliage Leaf 17 Transpiration 22 Absorption of Water by Plants 29 The Path of Water in the Plant : Structure of Stems 34 Mechanical Uses of Water in the Plant 42 Nutrition 45 The Occurrence of Carbohydrates in Plants 46 Formation of Carbohydrates 51 The Digestion of Starch: Translocation 54 Alcoholic Fermentation 56 Respiration 59 The Influence of External Conditions on the Plant ..;.... It was Louis Agassiz who said, ''If you study nature in books when you go out of doors you cannot find her." The posses- sion of this first-hand knowledge makes the reading of botanical books not only more easy, but vastly more interesting. The mental attitude of the true observer is that of a questioner. ' in water (100 ex.), or Pasteur's solution, made up as fo Uows: Pasteur's Ftr'':^::::io H Solution Grape sugar 15c c.c. Magnesium sulphate 2 grams Calcium phosphate 2 grams Potassium phosphate 2 grams Distilled water S3S c.c. — To ascertain what temperature change accompanies alcoholic fermentation. Place about 5 grams of compressed yeast in 250 c.c. After the test for CO2, test the air in both cylinders with a lighted splinter or taper, to see if it contains sufficient oxygen to support combustion. Polytrichum commune is widely distributed, growing in the soil in fields and woods. Naked-eye Characters: The Gametophyte (The ''Moss-plant") 1. Briefly describe the arrangement of the leaves on 1 With minor modifications the outline here given for the study of the moss will serve for species of Mnium, Funaria, or almost any other com- mon moss. Describe the margin of the leaf -blade (i.e., entire, notched, serrate, etc.), and the shape of its apex and base. Compare the form of the leaves in the same regions of the male and female plants. Then may follow the operation, that is, the arrange- ment of the materials and apparatus in a suitable way. Above a U things, it should be a record of your own observation, not of your neighbor's. (Note: The iodine is not the test; it is * only the reagent used.) Experiment 19. If time permits of individual tests by the student, microchemical tests may be made by mounting in water, on microscopic slides, small portions of, first, commercial starch; second, material scraped from any soaked seeds {e.g., corn, bean), a potato- tuber ( a stem), any convenient fleshy root, in each case observing (and drawing) the shape, surface- markings, and characteristic groupings of the starch grains, then running under the cover-glass a drop of iodine solution, and observing the color reaction. This last observation is often made more striking by placing the leaf on a small piece of glass, and holding it to the light. The chemical formula for a molecule of starch is Ce Hio Os. The mixture, properly made, has a clear blue color. OCCURRENCE OF CARBOHYDRATES IN PLANTS 49 If the Fehling's solution is not freshly prepared, it should be tested, before using, by heating a por- tion in a test-tube until it boils. — To demonstrate a test for the pres- ence of cane sugar. Proceed as in the preceding experiment, using cane sugar instead of grape sugar. From this experiment what do you know has taken place in the leaf gathered at night? (2) Underneath the epidermis a narrow, dark- colored region of h5rpodermal sclerenchyma. This step is frequently referred to as ^'set- ting up" the experiment. If, as may happen on rare occasions, it becomes necessary to use your neigh- bor's notes, always state the fact clearly and frankly in your own book. In writing your notes, the aim should be to give \ ^ TO THE STUDENT 5 such a clear account of what you have seen and done that anyone else who knew nothing of the subject could profit by reading them. Now place i or 2 drops of the iodine into the cooled, boiled starch mixture. — To see if there is starch in (a) seeds; ih) stems; {c) roots. Boil in water, in a test-tube portions of the above- mentioned parts of plants, and proceed with the 46 . If we combine with this molecule one molecule of water (H2O) we have a molecule whose composition is represented by the formula C6H12O6 [(C6Hio05)n H2O = C6H12O6]. Sugar, then, differs from starch in possessing relatively more hydrogen and oxygen in its molecule. If a precipitate of red copper oxide does not form the solution is good. The effect is due to the grape sugar reducing {i.e., taking oxygen from) the cupric sulphate in Fehling's solution, forming cuprous oxide 7. (3) Within the h^-podermal sclerenchyma the fundamental tissue fparenchjmia^ (4) Imbedded in the parenchyma two promi- nent elongate, dark-colored areas, the central sclerenchyma, or stereome (sometimes fused into one).

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