: Mast, Samuel Ottomar, Strueture and Physiology of Flowering Plants « 19076 “TAD 4 Ay | heat Ai MyS iy STRUCTURE AND PHYSIOLOGY OF FLOWERING PLANTS SLUDENTS GUIDE BY S.0O. MAST, PH. D. SER PROFESSOR OF BIOLOGICAL SCIENCE HOPE COLLEGE Price ©5 conts per copy, 20 eacno ior +en Or moro. HOLLAND, MICHIGAN PRIVATELY PUBLISHED 1907 Copyright 1907 ; S. O. MAST \ it { e he \ fi + a ( t ) s f = 2 ty ic in ile ‘atti ealite [¥\) T°) PREFACE. The following laboratory directions are intended to serve as the basis for an introductory course in biological science. A student of average adaptibility can complete the laboratory work here outlined in one hundred hours. The object in view in this course is to familiarize the stu- dent with scientific methods of study, to gradually introduce the microscope, and to teach the general structure, the life history and the more important physiological processes in phanerogams. Uusatisfactory results in beginning the study of plants and animals with such forms as Ameba, Paramecium and Spirogyra, led to the composition of these directions for the use of students in Hope College six years ago. They have been used every year since and have been revised and rewrit- ten several times. In revision especial emphasis was laid on the practical as well as the logical arrangement of experi- ments and other matter and on the needs and difficulties of students beginning the study of living beings, as observed in personally directing their work in the laboratory. After completing the laboratory work on any given sub- ject, the student is referred to literature selected from various PREFACE texts. One or more of each of these texts should be in the laboratory. This feature of the course is considered very important, since the student thus not only gets the best writ- ten on any particular subject, within his range of knowledge; but he also necessarily becomes acquainted with a number of authors and consequently gets a broader view of the subject than he would if only a single text were used. A course con- ducted along these lines should be accompanied by occasional simple descriptive talks and numerous quizzes. Students frequently fail to understand the significance of many plant structures and the meaning of experiments unless they are carefully questioned about them. Undigested laboratory work has but very little value. While these laboratory directions are intended primarily for college work, they have proved satisfactory in the hands of tenth grade students, and have been used with slight modifi- cations 1a a course given yearly during the past five years. Judging from results in this work I believe this method would prove both successful and economic in all biological work in high schools. The department library can be well equipped and maintained if each student contributes about half the cost of an ordinary text in these subjects. And after the course is well organized, certain students can be appointed to take charge of the library and thus relieve the instructor of extra work. 8. O. M. CONTENTS PAGE General Laboratory Directions... 056445 oe as tee eee 1 ees ee. 5. TOL RUL ROU AN Ra ED EEN EL AICS it Gh leah 2 Te Se eee ie leo eo ss alare eta cmciaie dl wore nanan aps cecil 20 es eee Reha siukc eye CMC AOL oa ua ee Ae eee Modified Plant Structures . LAU NLS USGS On AM [eo] ORE EO Ce OEE Oar nn NS Bn Nea RANE he sae. 50 UN STRUCTURE AND PHYSIOLOGY OF FLOWERING PLANTS. GENERAL LABORATORY DIRECTIONS. Be as quiet as possible while in the laboratory. Keep your table in order; do not write on it, or mar the surface in any way. Thoroly wash all dishes and apparatus immediately after using them, and return them to their proper places. Notes will be required on all work in the laboratory unless otherwise stated in your laboratory directions. See that your notes are as nearly perfect as you can make them with regard to neatness, diction, spelling, grammar, punctuation, and capitalization. Your notes should con- tain descriptions of what you do and see. Try to make your descriptions clear enough so that by reading them any one who knows nothing at all about your work could get a clear idea of what you are trying to describe. All existing facts should be put in the present tense. Use the third person rather than the first. Occasional quo- tations are admissible, but if anything is quoted use proper marks to indicate it. All notes must be written in ink, In correcting notes the following abbreviations will be used: Not definite, nd; not clear, nc; description be- fore name, dbn; incorrect with reference to, (1) subject ‘matter, °; (2) grammar, ¢; (3) diction, d; (4) punctua- tion, x; (5) spelling, s; (6) paragraph, p. Before correct- ing your notes always study the object described again. SEEDS. Common White Bean. In your work in the laboratory always select several apparently perfect specimens for study. Having selected several common white beans, study them carefully, aid- ing the eye with a hand lens, and describe one in detail. Whenever a description of an object is called for, de- scribe it with regard to form as a solid, size, color, sur- face characteristics (i. e., hard or soft, smooth or rough, glossy or dull), structure, composition, and relation to other objects, or as many of these attributes as possible. In measuring use only the metric system thruout the course. Note the scar near the middle of the straighter edge of the beans, a small elevation near one end of the scar, and a small hole near the other. The scar is called the hilum; the small elevation, the chalaza; and the hole, the micropyle. Describe each. The hilum marks the place of attachment between the bean and its stalk, the seed stalk or funiculus. Near one end of one of your drawing cards draw a bean as seen from the side, and again as seen from the straighter edge, twice natural size (x2.) You may shade your drawing if you understand shading, but if not, draw the outline only. Label your cards consecutively with Roman numer- als, I, II, III, ete., and all the figures on each’ card jane STRUCTURE secutively with Arabic numerals. Let your initials ap- pear in one corner of each card. Do not write on the cards with a soft pencil. Read the introductory chapter of Stevens’ Botany, pages 1-4, and Leavitt's Botany, pages 244-245. See also Ganong’s Teaching Botanist, page 165. As soon as you have completed your drawings ask the instructor to criticise them. Do this with all future drawings, unless otherwise advised. Structure—Study several soaked beans. What effect did the water have on their size, form, and surface mark- ings? Remove the seed-coats, two closely united. The outer is called the testa and the inner the endopleura; de- scribe both. Are the markings seen on the surface of the dry bean, in the testa or the endopleura? What relation does the chalaza, the hilum and the micropyle bear to the testa? All that is left of the bean after the seed-coats are removed is called the embryo. It is composed of two large parts, the cotyledons, a root-like structure, the radicle, and a small bud of leaves, the plumule. Describe each in detail. Are both cotyledons attached to the radicle? What is the relation in position between the point of the radicle and the micropyle? Is the testa in any way modified near the distal end of the radicle? How many leaves do you find in the plumule? How are they folded? Demonstrate this to the instructor by cutting and folding pieces of paper to represent the leaves. | Make a drawing (x2) that will show the plumule, radicle, and one cotyledon in their natural position. From the study of the bean it will be seen that the & SEEDS . embryo of a seed is really a small plant which has been arrested in its growth and is now lying dormant. We know from experience that under certain conditions, and certain conditions only, this small plant will develop into a larger one. What these conditions are, and what becomes of the different parts of the embryo, as well as the relation between the plant and its environment, we shall try to ascertain by experiments that are to follow. Each student will perform all experiments person- ally, excepting those preceeded by the word class or group, which will be performed by students selected by the instructor. All students will, however, make ob- servations on all class and group experiments and.write them un, just as tho they had performed them personally. Exp. 1: *In some moist soil plant three or four of each of the following seeds: bean, castor-bean, four- o’clock, corn, pea, maple, squash, and clover. Cover, the seeds with soil, approximately 2 cm. deep, and set them in a warm place. Keep the soil moist. Study the de- velopment of these seeds for two or three weeks, noting what becomes of the different parts of each variety; the time it takes each to come up, the development of leaves, the position of the leaves, opposite or alternate, the kind of leaves, simple or compound, netted or parallel veined, the kind of root system, tap or fibrous, etc. The roots are to be studied, at the close of the experiment, by * In writing notes on the experiments use the following headings and write a paragraph under each: 1. Description of Experiment. 2. Results. 3. Discus- sion of results. 4. Conclusions. The descriptions of the experiments should be brief and concise. It can frequently be best given in connection with a sketch of the apparatus used. The results must be recorded in detail. The discussion should be clear and logical and the conclusions definitely stated. STRUCTURE 5 pulling up the plants. Record the results of your study by writing a paragraph on each variety of seeds studied. Four-o’clock. (Mirabilis.) Thoroly study Four-o’clock seeds externally. Do you find a hilum. micropyle, and chalaza? Carefuily remove the hard covering (testa) from a soaked seed. What are its characteristics? Do you find an endo- pleura’) di so,.describe.’ Note the leat-hke structure, a cotyledon forming a partial outer coat of the embryo. Remove it carefully. Do you find other cotyledons, a radicle, a plumule? Occupying the central portion of the seed is a white mass of substance called endosperm. After you have carefully worked out the form, size, color, structure, and interrelations of the different parts of the seed, demonstrate the results of your study to the in- structor. No notes on the Four-oclock seed will be required. Cut an entire seed, which has been soaked, cross- wise near the middle, and draw it as seen from the cut surface (x4). Remove the testa from another seed, cut it lengthwise thru the radicle, and draw as seen fram the cut surface (x4). Read Gray’s Lessons of Botany, pages 22-20. Indian Corn. (Zea Maize.) Carefully study, several kernels, of ‘corn, dry, and describe one. On the material table you will find some corn which has been soaked two or three days. Remove the outer coat from a kernel. This coat is really. com- posed of two coats very closely united. The inner is the testa, the outer is known as the pericarp. Describe. 6 SEEDS That part of a kernel which remains after removing the coats, consists of a creamy colored embryo, seen on one of the broad flat surfaces, and endosperm, which par- tially surrounds the embryo. Separate these two parts and describe each. The embryo is composed of a single cotyledon, a radicle, a plumule, and a rudimentary stem, the caulicle. The radicle, caulicle and plumule are imbedded in the flat surface of the cotyledon and can be only faintly seen. Lay these structures bare by removing parts of the cotyledon with your needle. The radicle, sur- rounded by a thin membrane, the root sheath, points toward the smaller end of the kernel, the plumule toward the larger, and the caulicle lies between these two. Which of these three structures is attached to the cotyledon? Cut thin cross sections of the plumule, cover them with water on a slide, and trv to work out the structure with the aid of a hand lens. Cut an entire kernel lengthwise thru the middle of the embryo perpendicular to its flat surface, and draw it as seen from the cut surface (x2). Make three cross sections of a kernel, one thru the plumule. one thru the caulicle, and one thru the radicle, and draw each (x2). Making use of your experience in studying the bean, four-o’clock and corn, work out the structure of the following seeds: pea, squash, clover and castor-bean. The enlargement found on one end of the castor- bean is known as the caruncle. On the side of the caruncle next to the flattened side of the bean you will find a small dark projection, the hilum. From the hilum to the opposite end of the bean note a small flat ridge, EXPERIMENTS a the raphe, and at the end of this ridge a slight elevation, the chalaza. The castor-bean has two cotyledons which are very thin and leaf-like. They are surrounded by endosperm. No notes will be called for on these seeds, but you will demonstrate the results of your study on each variety to the instructor, and make sufficient draw- ings on your cards to represent the structure. Put the drawings of the pea on a card by itself. Outside the laboratory study as many other seeds as you can conveniently get, e. g., apple, pea-nut, cherry, orange, etc. No notes or drawings will be called for on these seeds. Literature. Spalding: Introduction to Botany.............. ccc cece eee 13-19 Gray: Lessons and Manual of Botany........... 117-125, 125-128 Rood.) BOtAM YANG) WIOTISO. 6:6 o's s.ibiw ee oe EUs olrele wileteta eee ale 58-60 Exp. 2: Plant ten peas in moist sawdust, in a flower pot. Cover the pot with a glass plate, and keep it on your table in a temperature of about 22 degrees C, 70 de- grees F. Study the development of the peas from day to day. As soon as the radicle breaks thru the testa, draw one of the peas and the same pea again when the plumule breaks thru. These drawings of the pea and those that follow are to be put on the card which con- tains a drawing of a soaked pea. When working with seedlings always keep them in water as much as pos- sible and handle them with great care. After the radicle of the pea, which was drawn, is about 1.5 cm. long, select two other peas with radicles also about 1.5 cm. long. From one of these carefully remove one coty- ledon and from the other both. Ask the instructor for 8 SEEDS a piece of wood or cork (5x 5x7 cm.) containing three small holes, float it in a liter can nearly full of water, and put the radicles of the three peas selected thru the holes so that they will extend into the water. Put up some- thing for the peas to climb on as they grow. Make two more drawings of the pea with both cotyledons; one when the lateral roots appear, and the other when the leaves appear. What is the effect of removing the coty- ledons? After you have arrived at a conclusion, add about Io c. c. of culture fluid to the water and watch the development of the plants for several weeks longer. Exp. 3: Plant several peas in perfectly dry sand. Examine them after four days. Results ; conclusions? Exp. 4, Class: On a piece ot slate about) 22a ne cm. lay a piece of carpet paper just large enough to cover it. Cut two strips of the same paper 3 cm. wide and 25 cm. long; fold them in the middle, lengthwise, and cover the two longer edges of the carpet paper with them. Scatter a dozen or more sunflower seeds with the shells removed, some kernels of oats, and a little clover seed on the paper from end to end, and cover them with a glass plate as large as the slate. Use patent adjustable pinch cocks, test tube holders, or spring clothes pins to hold the plates together, and set one end of the plates into water approximately 2 cm. deep, so that they will be perpendicular to the surface of the water. Study this experiment from time to time for about a week. Results; conclusions? Exp. 5, Groups of Two: Mix fifty soaked peas with an equal amount of small pieces of moist EXPERIMENTS 9 blotting paper and put them into a 50 c. c. wide mouthed bottle. Close the bottle loosely with a cork containing a hole large enough to pass a thermometer thru, and set the bottle into a 4 liter can. Cover the can loosely with a glass plate or a can cover. When the radicies of the peas are approximately 1 cm. long, partially re- move the cover of the can carefully, and take the temper- ature of the air in it and also of the peas by thrusting the thermometer into them without removing the bottle from the can. Likewise take the temperature on each of the three following days. The temperature should be read as late in the afternoon as nossible. Results; conclusions? Exp. 6, Groups ef Two: Carefully remove the shells from twelve sunflower seeds. Put six in each of two elean) bottles which’ hold 16 (to 20 ¢: ¢, “Partly. fill one of these bottles with tap water, but do not cork it. Fill the other bottle entirely with water that has been heated to the boiling point and then cooled without being shaken, and cork it air tight. (Note that much of the air in solution in the water is driven off by heating). Keep these bottles on your tables several days or longer. Results; conclusions? Msp. 72) ul a large, test-tube or’ 2) 50) ta; 75) & ‘: wide mouthed bottle which is comparatively tall, about half full of water; mark the level of the surface by tying a cord around the tube or bottle and then add 25 dry peas.. Be sure to remove all bubbles of air clinging to the peas, and then record the level of the water again. Set the peas aside for 24 hours and then note the level of the water. Pour the water and peas into a dish, return the water without the peas to the tube or bottle, and record 10 SEEDS the level of the water. What is the relation between the increase in the volume of the peas and the decrease in the volume of water? What causes the peas to become larger? Exp. 8: Mix the 25 peas used in the preceding ex- periment with small pieces of wet blotting paper and put them into a 50 c. c. wide mouthed bottle. Close the bottle tight and set it aside until the peas have radicles about 6 mm. long. Carefully open the bottle and insert a burning splinter, also insert a burning splinter into a similar bottle without peas. Results; conclusions? After the splinter has been inserted close the bottle air tight and compare the growth of the peas in this bottle with that of those in the open bottle used in exp. 5.’ Exp. 9, Class: Obtain four 50 c. c. wide mouthed bottles, an 8 to 15 liter bottle, a small bell-jar with an opening at the top, and rubber stoppers with two holes each, to fit all the bottles and the jar. Run a glass tube thru each hole in the stoppers; one should extend to the bottom of each bottle, the other only a short distance beyond the lower surface of the stoppers. Set the bell- jar into an open dish containing water several centimeters de‘ p, and connect the glass tubes with pieces of rubber tuLing so as to make an air tight series consisting of two of the 50 c. c. wide mouthed bottles, then the bell- jar, then the two remaining small bottles, and finally the large bottle. Fill the large bottle entirely with water and the four small bottles about one-third with clear lime water, Ca(OH)2. Procure a wide mouthed bottle nearly 10 cm. high, containing vigorously grow- ing pea seedlings with radicles about one centimeter long, EXPERIMENTS 11 and place it under the beil-jar. Now siphon the water out of the large bottle by fastening a rubber tube to the elass tube which extends to the bottom of the boitle. After the water has run long enough to replace nearly all the original air in the bell-jar with air whicn has passed thru lime water in the first two bottles, close the rubber tubes leading from the bell-jar with pinch cocks and change the lime water in the two small bottles near- est the siphon, making sure that it is clear. Now fill the large bottle with water and siphon it off drop by drop so as to force the air thru the apparatus very slowly. The flow of water can be nicely regulated by means of an adjustable pinch cock. After the apparatus has been in operation several hours, note changes in the lime water. (a) Results with peas under the jar. I. In strong diffused sunlight? 2. In total darkness? ‘ (b) Results with a frog under the jar? Conclusions? Draw the apparatus in outline side view. Exp. 10, Class: Put 10 or 12 soaked peas mixed with moist pieces of blotting paper into a 50 c. c. wide mouthed bottle. After the radicles have broken thru the testa and are growing rapidly, take another botile of the same size and fill it nearly full of water. Bend a 3 or 4 mm. glass tube in the form of a U large enough so that one arm can be put into each bottle. Pass one of the arms thru one of two holes in a rubber stopper in the bottle containing the peas, and the other thru a hole in a cork in a small test-tube containing an opening 12 SEEDS in the bottom. Insert a thermometer into the bottle containing the peas and see that the bottle is air tight. Raise the temperature to 24 degrees C. by firmly grasp- ing the bottle in the hand, and then record the level of the water in the test-tube. Twenty-four hours later raise the temperature to 24 degrees C. again and record the level of the water. Has the volume of the gas in the bottle changed? Conclusion? Exp. 11, Groups of Four: Select a tall wide mouthed bottle and put 25 peas into it after they have) been in water 12 to 24 hours. Lay the bottle over and dis- tribute the peas equally along the side from top to bot- tom. Now cover them with a strip of moist blotting paper and fill the bottle with moist sand, packing it enough to hold the seeds in place as you put it into the bottle, and set it into a depth of about 6 cm. of running hydrant water, or water kept cold with ice. As soon as the peas begin to germinate, insert a thermometer into a hole in the soil near the peas and ascertain the tem- perature of the lowest peas germinated. Some students will use soaked corn, others soaked wheat, clover, or beans, in place of peas, but every stu- dent will take note of all the experiments. Results; conclusions ? Exp. 12, Class: Procure a thin glass flat bottom dish approximately 2 cm. deep, and a large flat cork to fit it. Fasten the shaft of a clinostat to the center of the larger flat surface of the cork and cover the opposite surface of the cork and the sides of the dish with blot- ting paper. Select six peas with straight radicles 5 to Io mm. long and fasten three to the cork near the perifery EXPERIMENTS 13 by thrusting pins thru the cotyledons. ‘The radicles must be parallel with the flat surface of the cork and must point toward its center. Arrange the clinostat so that the surface to which the peas are fastened 1s ver- tical. Moisten the blotting paper and cover the peas with the glass dish. Fasten the remaining three peas to a piece of wood, previously soaked in water, so that the radicles point in different directions, and place them in a damp chamber in such a position that the surface on which the peas are found is vertical. Wind the clinostat every day and keep it running a week. The rotation neutralizes the effect of gravitation. Explain how this is done. Results; conclusions? Exp. 13, Class: Pour mercury into a tumbler to a depth of about 2 cm., then add water about 3 mm. deep. Fasten two peas with straight radicles about 1.5 cm. long to a piece of water-soaked wood tightly wedged in the tumbler in such a position that the radicles form an angle of about 30 degrees with the surface of the mercury and their tips extend to within about 2 mm. of it. Do the radicles grow into the mercury? Conclusion? Exp. 14, Class: In a wire basket nearly filled with wet sawdust plant a dozen peas and as many kernels of corn, so that they will lie about 1.5 cm. from the bottoin. Now set.the basket in a mioderately damp place in such a way that the bottom will make an angle of about 45 degrees with the horizontal. Study the effect of moisture on the direction of growth of the radicles after they extend thru the bottom of the basket. Results: conclusions? Exp. 15, Groups of Two: As soon as the plants in 14 SEEDS exp. I come up, cover some of them with an opaque jar so as to exclude all light. Study these plants from day to day for a week or more. Results; conclusions? Exp. 16, Class: This experiment is intended to show which chemical elements are necessary in the soil in order to insure normal development in green plants. Plant a small handful of corn in a flower pot con- taining sawdust and keep it in a warm place where ger- mination will take place rapidly. Procure nine jars holding one liter each and flat corks large enough to fit them. Put four holes about 2 mm. 1n diameter thru each cork and pass a glass tube about 10 cm. long thru one. Wash the jars, corks, and tubes in a weak solution of hydro- chloric acid, rinse them in water, then sterilize them by immersing in boiling water, and finally wash them in dis- tilled water. Fill the jars nearly full of distilled water and label them 1, 2, 3, etc. To the water in jar No. 1 add the following compounds and label it “All”: Potassnit, Mtrate. 00. 244 ike I gram. Calcium -sullate 26. 446% bes 0.5 gram. Nagwesum) siliate: ese. ccs eR 0.5 gram. Calcium phosphate (pulverized)..0.5 gram. Sot ahbord. . eek i ie ae 0.5 gram. Chlorid of iron (weak solution)...0.5.¢. c. Note the elements found in these compounds. Jar No. 2.—Add to the water in this jar the same coinpounds as were added to No. 1, but add sodium nitrate in place of potassium nitrate. Label “All minus potassium.” EXPERIMENTS 15 Jar Nc. 3—Same as No. 1, excepting potassium phos- phate in place of calcium phosphate and omit calcium sulfate. Label “All minus calcium.” Jar No. 4—Same as No. 1, excepting magnesium chlorid in place of magnesium sulfate, and omit calcium sulfate. Label “All minus sulfur.” Jar No. 5—Same as No. I, excepting omit calcium phosphate. Label “All minus phosphorus.” Jar No. 6—Same as No. 1, excepting omit magne- sium sulfate. Label “All minus magnesium.” Jar No. 7—Same as No. 6, excepting potassium chlorid in place of potassium nitrate. Label “Ali minus nitrogen.” Jar No. 8—Same as No. 1, excepting omit iron chiorid. Label “All minus iron.” Jar No. g—Omit all chemicals. Label “distilled water.” After the corn seedlings planted in sawdust have plumules about 2 cm. long, select 27 vigorous speci- mens, put them into water as soon as taken from the sawdust, handle them very carefully, remove all particles of substance clinging to the roots, with a camels hair brush, wash them thoroly, and rinse them in distilled water. Push the plumule of a seedling thru each hole in the corks from below, and fasten it by filling the space around it with cotton. Fill all crevices around the corks with cotton and plug the upper end of the glass tubes. Wrap opaque paper around the jars, fasten it so as to exclude all light, and put the labels on the outside. Set these jars where they will be in direct sunlight at least part of the dav. Replace the water evaporated by adding 16 SEEDS distilled water, thru the glass tubes once a week or oftener if necessary, and study the development of the plants until the close of the course. Results; conclusions? Literature. Spalding: Introduction to Botany...5.. 00... 5.20000 cee 23-28 Leavitt: Outlines of Botany. .360..00.0506 i eo eee 15-23 Coulter: .Text-book:of Botany ?:. os... 63009 Sa eee 84-97 Stevens: Introduction to Botany..........% >. sc6e.. a. ase 16-27 Histology of Seeds. Ask the instructor for a pea that has been in glycer- in for some time. With a sharp razor cut thin cross sections of one of the cotyledons, put them on aslide, add a few drops of 50 per cent glycerin and cover them with a cover-glass. Study the sections carefully with the low power and note that they contain numerous holes, many of which are filled with granules. These holes are known as cell-cavities, and the substance between the cavities composes what is known as cell-walls. A cell cavity with its contents, surrounded by a cell wall, constitutes a cell. All cells, however, do not have a wall. Find a thin place in one of your sections, move it to the center of the field, carefully turn on the high power, and . study the cells. You will find granules of various sizes in them. The large ones are starch granules and the very small ones proteid granules. Turn on the low power, remove the slide from the stage, add a drop of dilute iodin to one edge of the cover glass and apply a piece of blotting paper to the opposite edge until the iodin has been drawn under far enough to reach some of the sections but not all. Now study the sections both under HISTOLOGY 17 the low and the high power. What is the effect of iodin on starch granules; on proteid granules? Is the proportion between starch and proteid the same in all cells? Study particularly those near the outer surface. Accurately draw three or four typical adjoining cells in outline as seen under the high power and represent the granules in one of them. Cut sections perpendicular to the cross sections already cut and study them as you did the cross sections. From these two series of sections you should get a clear conception of the form of the cells as solids. Describe the microscopic structure (histology) of a cotyledon of a pea, Find some starch St anule: not in the cell-cavities. How can they get out of the cavities? Under the high power study the structure of some not stained with iodin. Make an enlarged drawing of a typical specimen showing the marking in it and describe. Making use of the experience gained and the labo- ratory notes used in working out the cell structure of a cotyledon of a pea, study the histology of the following seeds: bean, corn, wheat, oats, soaked in water about 12 hours, and sunflower 4 and castor-bean not soakea, and also that of a potato, which is not a seed. Make © drawings similar to those made in studying the pea. Note the relative amount of starch and proteid in each seed, form, relative size of the cells and thickness of the cell-walls, etc. In which part of each seed do you find most proteid; most starch? The sunflower seeds and castor-beans contain oil. Mount some sections of these seeds in water and others in glycerin. While studying 18 SEEDS one of the sections in water under the low power, press the cover-glass lightly with a needle directly over the section, and note that globules of oil ooze out. Do you find any starch or proteid? Crush a small piece of both seeds on glazed paper with your scalpel and note the oil. What is manufactured from castor-beans? Mention sev- eral other seeds that contain oil. Cut sections of a cotyledon of a pea or bean, the stem of which is 20 to 30 cm. long. What changes have taken place in the cells and their contents? Starch granules which are considerably corroded may frequently be found. Draw one. Ask the instructor for six unknowns, each of which may contain one or more of the different kinds of starch you have studied, and also proteid. Ascertain the con- tents of each. Record your results and report to the instructor. Mount a few cotton fibers, Note that each fiber is composed of a thin long cell, containing a very small cavity and a thick cell wall. The wall is composed largely of a substance called cellulose. Add strong iodin. What effect does it have on the cells? Remove the iodin with blotting paper and ask the instructor to add a few drops of 75 per cent. sulfuric acid. Be exceedingly. care- ful not to get acid on the microscope table, cleaning cloth, or hands or instruments. Study under.the low | power only. How does the acid affect the color of the cell walls? What is the final effect of the acid on the cells? When a substance takes on the color you obtained in the walls of the cotton fibers after adding iodin and sulfuric acids it contains cellulose. SS orn HISTOLOGY 1)? With a sharp scalpel (not your razor) cut thin longt- tudinal sections irom the endosperm of a date seed, paral- iol with the surface opposite the groove in the seed. Mount them in water and note that the ceils contain thick walls and small cavities. Draw two or three an: test the walls for cellulose. Literature. bereen: ( Miements Ob Otani ialis 68 oa Sd oP aw eee © oe 4.7 Berson: VFoundations Of Botany. so. 6 oe ce ei 6 we a eid eee ole 8-35 Berscen and Davis: Principles of Botany ..0.0...8 5. sobs eee 415 Kerner and Oliver: Nuaturai History of Plants....... See INnGEx Distribution of Seeds. Make a study of the following seeds with a view to discovering the method by which Nature acomplishes their distribution. Illustrate the form of the seeds and their appendages by means of drawings. Describe the method of distribution for each variety and give your judgment as to the efficiency of each method. Milk- weed, maple, sand-bur, burdock, catalpa, witch-hazel. Literature. eereen- Woundations of Botany... oc es eee ses we Greeny 373-395 Bereem: “OMlements Of BOLAMYV. | sca Ws oo anes s oc elee eels 191-199 Atarsou:;: mlementary Bovany. sv. yess ok ee ew eee 458-463 ees are ae EG. aig PE Se oe! ook ke a a yee Boe bakes 361-368 Coulter: DAME MERCATOR Sus onl Cigna, BeOS oR Ae Eyles 113-122 UCU PROBATE Woe ae iclle hovatas Wie! 6 wid aueiaete.e ee pobie des atone oa 158-163 Ca es PASCO DIS OTS Ue Me oars Gls Gi well ore Je Mies cau ea eg Meu ee ase 1-87 Avebury: Flowers, Fruits and Leaves..........cccccecccees 52-96 > : STEMS. Es i Dicotyledonous Stems. The stem is that portion of a plant which connects the roots with the leaves. It bears leaves and conse- quently must contain buds. Thoroly inspect a horse-chestnut twig about 40 cm. long. The twig has several buds and is consequently a portion of astem. What is the general character of the bark? How does it differ in different parts of the twig? Note the horse-shoe shaped scars, leaf-scars, What are they caused by? Are they alternate or opposite? Note the dots on the leaf-scars? Does the number vary in different scars? The instructor will explain, to the class as a whole, what has caused them. That portion of the stem directly underneath a leaf-scar is called a nede; the portion between two consecutive scars an internode. Are the internodes of different twigs and portions of the same twig grown in different years the same in length? Rings composed of small narrow scars, scale-leaf- scars, will be found on the twigs. Remove the scale leaves which surround a terminal bud one by one. How are they arranged, alternate or opposite? How many are there? What do you find in the bud? What plant structures develop from buds? Can you now ascertain what causes the rings above mentioned? How many terminal buds develop in a twig in a year? How old is the twig studied, at its larger end? How many centi- DESCRIPTION pI meters has it grown each year? Compare the growth of last year in several twigs. Is it the same? The smaller buds along the side of the twig are called lateral buds. Is there any definite relation in posi- tion between buds and leaf-scars? Lateral buds develop into branches. Do they all develop? Are the branches of horse-chestnut opposite or alternate? Does the ar- rangement of the branches depend upon that of the leaves? Why? Sketch the last two years growth of your twig (x1) and describe it in your notes. Study the beech twig as you did the twig of the horse-chestnut, using the same outline. Draw and de- scribe the last two years’ growth. The dandelion is a so-called stemless plant. Pull one up by the roots, and remove the leaves one by one, beginning at the bottom. Does the plant have a stem according to the definition of stems? If so, how long is it? How old is the plant studied? As soon as the pea grown in the culture fluid is large enough, study the stem. Is it cylindrical? How thick is it at the bottom; near the top? Does the plant have lateral buds? Note the terminal bud. Is it pro- tected by scale leaves? Ji not, why-not? ‘The feaves are compound. (See Bergen, Elements of Botany, pages g1-93.) Are they opposite or alternate? Can the stem support itself? Is there anything gained by having the stem so small at the bottom? Study the stem of a climbing bean or morning glory, following the outline for the study of the pea stem, and ascertain, if possible, how it climbs. 22 STEMS Ask the instructor for alcoholic specimens of Solo- mon’s-seal. Be careful not to injure alcoholic material in any way. Study it under water, and do not let it get dry. A portion of the stem of this plant grows underground, in a horizontal position. Do you find buds, leaves, scale leaves, or scars on the underground portion? Why call ita stem rather than a root? On the upper surface of the underground stem note several pits. What has caused these pits? How many are there? Is there any rela tion between the number of pits and the age of the stem? Describe and draw the last two years’ growth of the underground stem (1x), side view. Procure a medium sized potato. Is it a stem or a root? How is the potato attached to the rest of the plant? Note the pits (eyes) on the surface. How many are there? Where are they most numerous? (A vew small projection is sometimes found in each eye on the border, nearest the attached end of the potato. This projection is homologous with a leaf. Near the middle find a small elevation (a bud), sometimes several. Study the eyes under a hand lens and draw one. Make an outline drawing of a potato and show the distribution of the eyes. Put a portion of a potato containing several eyes in a damp chamber, set it in a warm place and watch the development of the buds from day to day. Where do the roots come out? Outside the laboratory study as many other stems and buds as you can—the onion or hyacinth, the cactus, the oak, the pine, the lilac, etc. Nothing need be written about these, but you will be expected to answer ques- tions concerning them. DICOTYLEDONOUS 23 Literature. eae Ot CS! Of, IZ0UANY. oo Bees sles wiciGiala's 016.0 ai eile 3.0 @ a sce 51-66 Seaiaiwe:! LO troOducliOn,. tO BOUADY . 5.0 siete oes tec oes 0's eas 52-56 Member an TOLAUIONS 6 Flic so oo alee w ee slcpie oie ood ses Seb gle « 3-82 Percen and avis: Principles’ of Botany... 0265.2 c ee 4S 56 PETES ine ROU INN So ok eae Salant aldveuan dS ul bse Sable end okies hme 365-882 tray. Wessors and Manual of Botany... ssc... <6 see os et 27-48 Perse) MIC Ments : OF, BOCAIMY « o.e). Vee) alscaie os 010s, c1e. 6 see. © sim win 2 38 o1 ipeneem 7. Woundalions: OF ISOTANY. 46 vce cece eo wae ores 2 oe 62-43 siraspurger: Text Book of Botany........5..+.-.-+---20- 18-27 Kerner and Oliver: Natural History of Plants, Vol. 1....655-724 Structure of Dicotyledonous Stems. With a sharp pocket knife or scalpel cut cross sec- tions of a horse-chestnut twig three years old. Place the sections, which should be about 5 mm. thick, on a slide in some water and study them under the dissecting micro- scope. Observe that the stem is composed of a central portion, the pith, which is surrounded by two layers, one of wood and one of bark. How thick is each of these layers ?- The bark is composed of two layers, a brown layer on the outside, and a green layer next to it. What is the relation in thickness between these layers? Lines radiating from the pith may be seen to extend to the bark. These lines are called medullary rays. li they cannot be readily seen in horse-chestnut, look for them in cross sections of a beech twig. About how many do you find? Are they all of the same length and thickness? They are distinctly seen in quarter-sawed oak. Ask the instructor for a specimen. Wood tissue is composed of concentric layers, ar- ranged around the pith. How many are there in the 24 STEMS twig under observation? ‘They are more clearly seen in elm than in horse-chestnut. Cut an elm twig about I cm. in diameter, off 3 or 4 cm. above and the same distance below an annular scale-leaf-scar ring. The layers can be seen better if they are cut obliquely. See that the cut ends are smooth. Let them dry a few minutes. How many layers of wood do you find above the annular ring; how many below ? What does this fact teach? Nu- merous small holes may be seen in the layers of wood. In which part of each layer are they largest? Can you account for this? Have the instructor explain. Make an outline drawing of a cross section of a horse- chestnut stem (x2). Cut cross sections of the following stems, similar to those cut of the horse-chestnut; study these sections as you did those of the horse-chestnut, and make an outline drawing of each: beech, elder, and geranium, or any stem that has grown this year, and butternut or walnut. The central portion of the butternut or wainut stem will be found to consist of dark colored wood. This is called heart wood; it is dead. The light colored wood sur- rounding it is living and is called sap-wood. Note the surface character of the bark (brown bark) on all the different trees on the campus. What causes it to become much rougher as a stem becomes thicker? Does any fall off from year to year?- How is it replaced? Peel some of the brown bark from a cherry twig. Note the white spots on it, called lenticells. Do they vary in form in different parts of the stem? What causes this difference in form? Exp. 17, Groups of Two: Place three pieces of wil- DICCTYLEDONOUS 25 low stem about 1.5 cm. in diameter and 15 cm. long into a 2 liter can containing water 2 cm. deep. Carefully take a ring of bark 8 mm. wide from one stem so that the lower edge of the ring will be 5 mm. above the water. See that this stem and one of the remaining are right side up and the third upside down. Cover the can and put it in a warm place (23 degrees C.) Roots will develop on these stems. How long does it take them to start? Where do they come out with reference to the leaf-scars? With reference to the region from which the bark has been removed? After having learned all you can about this experiment have the instructor ex- plain its meaning. Histology of Dicotyledonous Stems. As soon as you have finished the following study of the histology of the dicotyledonous stem, describe the ells cf each kind of tissue with regard to form as solids, color,-relative thickness of cell-walls, character of cells and contents, and also, judging from the structure of the cells and their contents in each kind of tissue, give the function of each. With a sharp razor cut very smal! thin cross sec- tions from a beech twig one year old. Mount them in water and study them under low power. Identify the bark (brown and green), wood layers and medullary rays, and pith. Find a very thin place near the edge of a sec- tion and study it under the high power. Note that the cavities of the cells in the brown bark are filled with brown substance. Draw four or five adjoining cells. Arrange your drawings of the cross sections so that there 26 STEMS will be room next to each, for drawing of longitudinal sections of similar tissues. Ask the instructor to correct your drawings on the histology of the stem, while the section drawn is still under the microscope. The cavities of some of the cells in the green bark contain numerous granules calied chloroplasts. How do the cell walls of these cells compare in thickness with those found in the brown bark? Draw three or four cells and fill in one of them. In the green bark near the wood tissue you will find patches of light colored cells, bast fibers. These cells are ciosely packed together. ‘They are smaller than the green cells, have thick walls, and cavities so smali that they appear like mere dots under the microscope. Draw three or four. Between the wood and bark is found a thin layer of tissue composed of thin flat cells. This layer is known as the cambium region. It can be most clearly seen in rapidly growing stems because the enlargement of the stems takes place in this region. The instructor will demonstrate how growth takes place, to the class as a whole. Draw a few cambium cells. The woody tissue is composed of three kinds of cells, wood-fibers, which appear in cross-section some- thing like bast fibers; vessels, containing large cavities which appear like definite holes thru the section; and medullary ray cells, which are much like pith cells, con- siderably elongated. Draw two adjoining vessels so as to represent the relative thickness of their walls, three or four wood fibers and medullary ray cells, and also afew pith cells. Test the cells in the stem for starch and cellulose. In which do you find starch; in which cellulose? DICOTYLEDONOUS Zh Select a short piece of stem one year old; split it in half, and cut Icngitudinal sections from the split surface. Study these sections carefully, with the low and high power and identify all the different kinds of cells seen in the cross sections by referring to their relative position. Many of the vessels have elongated pits running trans- versely in their walls. Bast fibers and medullary ray cells will not be found in every section. Why not? The medullary ray cells appear somewhat like brick-work. In connection with your longitudinal sections study macer- ated tissue, which the instructor will prepare for you. In macerated tissue a side view of the fibers and vessels will be seen. This is, of course, much like the view ob- tained in long. sections. Draw three or four cells of each different kind of tissue found in longitudinal sections ex- cepting fibers and vessels. Make a detailed drawing of a portion of a wood fiber, a bast fiber, and a vessel as seen in macerated tissue, and another outline drawing of a few adjoining cells of each kind showing how they are united. Exp. 18: Place the cut end of an elder and a beech twig containing several leaves into a weak solution of eosin, also the proximal end of a rather long potato with a little of both ends cut off. After 24 hours make cross and longitudinal sections of the stems with a scalpel. Study these sections, the cut surfaces, and also the leaves. What conclusions can you draw? Do you find any woody tissue in the potato; any vessels; bark; pith? Razor sections may prove advantageous in studying the potato. 28 STEMS NMonocotyledonous Stems. Exp. 19: Piace the cut ends of two Trillium or man- drake stems into a weak solution of eosin. After 24 hours make cross and longitudinal sections of the stems with your scaipel. The structures thru which the eosin rose are called fibro-vascular bundles. Do you find them equally distributed thruout the stem? How long are they? Beginning at the cut end, trace several Siete bundles as far up the stem as possible. Do they branch? Where do they end? ‘This can be ascertained by study- ing a small piece of a leaf under the low power. Describe the distribution of the coloring matter in the leaves. Con- clusions? Monocotyledonous stems are composed of scleren- chyma fibres forming a hard rind around the outside, fibro-vascular bundles scattered thruout the stem, and pith filling in the spaces between the bundles. Note these tissues under a hand lens 1n cross sections of a corn stem, and make an outline drawing representing their distri- bution. Histology of Monocotyledonous Stems. Make very thin cross sections of a piece of a corn stem preserved in alcohol. Study them under the high power and draw three or four sclerenchyma fibers and as many pith cells. The fibro-vascular bundles of the monocot stems are homologous with the wood and bark ot the dicot stems. They are composed of two kinds of tissue, xylem and phloem. The xylem is homologous with the wood tissue of the dicot stems, and is composed of fibers and vessels. The three or four large openings MONOCOTYLEDONOUS 29 are cross sections of vessels; surrounding these there will be seen cross sections of the fibers. Are the walls of the fibers thick? Note their cavities. The phloem is homolo- gous with the bark of the dicot stems. It consists of a group of light colored cells, situated nearly between the two most prominent vessels. Are these cells all of the same size and structure? The larger ones are sievetubes. The cambium region is found only in actively growing stems. It is situated between the xylem and phloem. Surrounding the entire bundie are several layers of small thick walled cells forming the bundle sheath. Select a bundle in which the structure can be clearly seen and make an outline drawing of it about 7 cm. in diameter. Represent the phloem in outline and draw all the larger vessels and a few cells of each of the different kinds of tissue found, including large and small phloem cells. Ask the instructor to criticise your drawing while you still have the sections under the microscope. Let the instructor give you some macerated fibro- vascular bundles and rind. Find isolated cells (fibers and several kinds of vessels) composing these tissues, com- pare them with their cross sections already studied, and describe them with regard to form as solids, thickness of cell walls, etc. How are they joined to each other? Draw two or three of each of the different kinds of cells. Judg- ing from what you now know about the different kinds of cells in a monocot stem, what do you think the func- tion of each kind is? Is their structure well adapted to their function? Literature. meevecrs: Introduction to (Bettany, 20.6 eek Soe oe ecw kk. 55-74 30 STEMS Bergen and Davis: Principles of Botany.................. 56-74 Coulter: Text Book of Botany... 0 .c