Vessel Development and Structure

passing into net-like or reticulate HISTOLOGY 47 markings and the latter finally giving rise to pits ; draw a group of vessels showing the various stages of development from ringed to pitted walls ; 1. Have the vessels nuclei or contents? Do you find any cross-partitions? Any hint of their former presence? What is the purpose of the thickenings? How were they formed? -- Make the lignin test. (f. 20, p. 31.) Tracheids (33) 31. Pinus austriaca, Austrian pine: make transverse and both radial and tangential longitudinal sections of a young twig; the entire woody tissue, with the exception of the occasional medullary rays, consists of tracheids; draw a group of tracheids from each of the three sections, paying especial attention to the bordered pits in the walls; 1. The transection and the tangential longi- section will give a cross-section of the bordered pits; the radial longisection a front view of them. Explain the structure of the pits, especially the border. Do they occur in rows? Why? How many parts to the cell wall in the tran- section? Is there any suggestion of canals? Do the tracheids have contents? Sequoia sempervirens, redwood, (f. 23, p. 33.) ; 48 MANUAL OF BOTANY THE TISSUE SYSTEMS -- Epidermal system (40): Epidermis 32. Agave americanaj century plant : make thin transections of the epidermis of a joung leaf draw 4 or 5 cells, paying especial attention to the cuticle, the thick outer wall ; 1. Do you find a nucleus or plastids? Is there any protoplasm present? How is the outer wall thickened? Does it show layers? Make the cellulose and lignin tests. What are the outer layers? -- Stomata or breathing pores (44) 33. Agave americaiia^ century plant: in the sections made above, the epidermis shows openings into the interior of the leaf, which are guarded by peculiarly modified cells; draw one stoma, showing the epidermal cells, guard cells, and the parenchyma cells which surround the air chamber ; 1. What are the guard cells? What is their function? Do they make starch? Why? Are they closed or open in your section? Why are they thin-walled? What is the purpose of the chimney formed by the epider- mal cells? What is the purpose of the air chamber beneath the stoma? Does it have any connection with the spaces between the cells of the leaf? Stain with iodin. HISTOLOGY 49 34. Begonia sp., begonia: strip a small piece of epidermis from both surfaces of a leaf and mount in weak alcohol ; if there is sufl&cient difference to warrant, draw a group of stomata from each surface; 2. Compare the top view of the stoma thus obtained with the sectional view in the experiment above. Are the stomata single or in groups? Contrast the guard cells with the epidermal cells. Are any of the stomata open? Do the walls of the guard cells next the opening show any peculiarity? Why? Which has the larger number of stomata, upper or lower surface? Why? Under the low power count the number of stomata in a given space, (f. 29, p. 44.) -- Hairs (42) 35. Lycopersicum esculentum, tomato : jnount thin transections of the upper part of a young stem; note the three sorts of hairs, paying especial attention to the way in which they arise from the epidermal cells; draw a hair of each sort giving in detail its connection with the epidermis; 1. The largest hair may well be drawn to a scale of fori. Compare the origin and structure of the three sorts of hairs. From this can you suggest any explanation of their function? In 50, MANUAL OF BOTANY what way do the cells of the hairs differ from -- epidermal cells from soft tissue cells? (f. 26, p. 43.) Fibrovascular system (46); -- -- Collateral bundles Closed type 36. Zea maySj corn : mount thin transections of the stem; draw a complete bundle; 1. Distinguish the wood or xylem portion of the bundle from the sieve or phloem portion. Which is on the side toward the surface of the stem? Do you find any companion cells with the sieve tubes? What is the bundle sheath? Is it complete? Point out the various kinds of tissues which make up the bundle? Is there any meristem or growing tissue in it? What is the position of the -- bundles in the stem? (f. 30, p. 47.) Open type 37. Impatiens halsamina, balsam : mount thin trans- and longisections of the full-grown stem ; draw a bundle in both views, showing in the transection the ring of meristem or cambium, upon which the bundles are strung, at either side; 1. Compare the position in the stem of the open and of the closed type of bundle. What relation has the ring of cambium to this fact? Locate the xylem and phloem parts of the bundle. What kind of tissue separates them? Point out the wood fibers, tracheary HISTOLOGY 51 vessels, sieve tubes, etc. Which parts are lignified? Which are composed of cellulose? Do you find any young bundles? How do they arise? How are they different from the old ones? (f. 20, p. 31; f. 31, p. 48; f. 32, p. 49.) -- Radial bundles 38. Zea mays, corn : make thin transections of well-developed roots; make a diagrammatic sketch, showing the position of xylem and phloem in the bundle and a detailed drawing of a segment, showing the pith, two xylem and phloem rays, and the corresponding portion of the bundle sheath ; 1. How many radial bundles in each root? What is its position? Contrast the radial bundle with both types of the collateral. Is there any cambium in the bundle? (f. 33, -- p. 51.) Concentric bundles 39. Pteris aquilina, brake fern : cut thin tran- sections of the root-stalk; draw a small bundle or a portion of a larger one ; 1. Is there more than one bundle in the stem? What of their position? Is there any cambium present? Any sieve tissue? Compare with the radial bundle, (f. 36, p. 54.) Make diagrammatic drawings of the four transec* tions studied above, showing the relativ number and position of the bundles. 52 manual of botany -- Reduced bundles 40. Populus deltoideSj cottonwood : make thin superficial sections from the under surface of the leaf, cutting through some of the secondary veins; draw a segment from the reduced bundle thus exposed, showing the leaf parenchyma, mesophyll, on either side and the detail of the bundle; 1. Compare the reduced bundle with the longisection of the open bundle of Impatiens. What tissues and vessels are still found in it? Is the bundle sheath still present? Are the reduced bundles of the leaves connected with the complete ones of the stem? Point out why this must be so both structurally and functionally, (f. 37, p. 58.) Fundamental system (57): -- Intercellular spaces 41. Scirpus lacustriSj bulrush : make thin tran- sections of the stem ; note the extremely large intercellular spaces, across which are stretched thin plates or diaphragms of two � different patterns; draw an intercellular space with its walls and diaphragm, i, and a few cells from both sorts of diaphragms, 1. Compare these spaces with the small trian- gular spaces so common in soft tissue. Do you find connecting forms between the latticed and the stellate diaphragms? Is there an explanation of these spaces and HISTOLOGY 53 diaphragms in the fact that the bulrush is a water plant? Point out the tissues of the -- -- fundamental system, (f. 41, p. 63.) Secretory passages Resin canals 42. Piniis austriaca, Austrian pine : make thin transections of the leaf; the center is occu- pied by the fibrovascular system, the edge by the one-layered epidermis^ the remainder is * the fundamental system, in the chlorophyllbearing tissue of which are found the resin or turpentine canals; draw a canal showing the detail ; 2. How many tissues in the fundamental sys- tem of the pine leaf? What is the function of the fibrous tissue at the edge? How many parts in the canal? What is the purpose of the outer row of cells? What kind of fibers are they? What is the function of the cells next the cavity of the canal? -- Mucilage canals 43. Sagittaria latifolia, arrowhead: make a thin transection of the petiole; the mucilage canals are found where the walls of the in- tercellular spaces join; draw a couple of canals, showing their location and structure 14- From the spaces of the stem, in what sort of places must the arrowhead grow? Are there any diaphragms? Point out the different systems and tissues. How many parts to the canal? (f. 42, p. 63.) 54 manual of botany -- Cork (59) 44. Samhiwus canadensis, elderberry: make a thin transection of the stem through the raised corky masses or lenticels; draw the cork mass in the lenticel and the cork-pro- ducing meristem or phellogen just beneath; 1. Compare cork with parenchyma. Make the Why cellulose and lignin tests with it. is the lenticel filled with cork? What is the function of cork tissue? (f. 38, p. 59; f. 60, p. 39.) STRUCTURE AND CLASSIFICATION branch f�rotof�myta Class Schizophyceae ORDER CYSTIPHOREAE FAMILY CnaOOCOCCACEAE 1. Gloeocapsa arenaria: draw several colonies, showing the development from a single-celled colony to those having 8 or 16 cells ; 3. Are the cells all alike? Explain the layered wall. Why are the cells round or spherical? Do they show any of the usual cell contents? Can you distinguish a nucleus or a definite cytoplasm? How do the cells increase? Point out the differ- ent steps in the process. Do you find any move- ment of the cells? Compare the cell of this simple plant with an ordinary parenchyma cell. The plants contain chlorophyll though this is concealed by a blue green coloring matter called phycocyanin which is present throughout the entire branch. Each cell contains a single cylin- drical plastid; the granularity of the cytoplasm is due to granules of food material of uncertain composition, probably related to aleurone. (f. 60, p. 126; I, 3.) 56 MANUAL OF BOTANY ORDER NEMATOGBNBAE FAMILY NOSTOCACEAE 2. Nostoc commune: draw a thread showing the heterocysts and the different stages of fission in the vegetative cells, also the spores if any are present; 2. What is the character of the thallus or mass in which the filaments are imbedded? Is fission here essentially the same as in Gloeocapsa? In what way do the vegetative cells differ? Con- trast spores and heterocysts with the vegetative cells from which they are derived. Point out the steps in evolution by which a Gloeocapsa might have become a Nostoc. Show why the latter is higher. What other ways of increase has Nostoc besides the fission of its vegetative cells? (f. 61, p. 126:1,4.) FAMILY OSCILLATOEIACEAE 3. Oscillatoria tenuis: draw one or two threads, paying especial attention to the tip and to fission and noting the disposition of the granules ; 2. Do you find spores and heterocysts? Compare the fission with that of Nostoc. Explain the tip cell. How many movements have the filaments? Show how in one sense Oscillatoria is lower than Nostoc; in another higher. Does it have a definite thallus? In addition to fission, propagation occurs by means of the breaking up of the filament into short pieces which slip out of the thin sheath and grow into new filaments. These STRUCTURE AND CLASSIFICATION 57 bodies are called hormogones and are often seen forming in the filament, at which j>oint the thin sheath usually becomes visible, (f. 61, p. 126: I, 16.) FAMILY SCYTONEMATACEAE 4. Scytonema cinereum: draw a portion of a thread, showing one or two false branches and the heterocysts, also the sheath and different stages of the vegetative cells ; 2. Point out the differences between Scytonema and Oscillatoria. Do these filaments move? Does the presence of a thick sheath explain this at all? Are there any spores? Hormogones? Why do we speak of false branching? Show why Scytonema is higher than Oscillatoria and Nos- toc. What sort of a thallus does it form? (II, 24.) FAMILY RIVXJLABIACEAE 5. Gloeotrichia piswn : draw a complete thread, showing especially the vegetative cells which are un- dergoing fission; 1. What sort of a thallus has this plant? Is it like any you have had? How are the filaments ar- ranged in the thallus? Does the thread move? Why? Does it have spores and heterocysts? Does fission occur anywhere in the thread or at a definite place? Why? Explain the long cells of the lash at the tip. Do they divide? What of the sheath ? Show how a Gloeotrichia might have developed from a Scytonema. (Ill, 33.) 58 MANUAL OF BOTANY FAMILY BACTERIACEAE 6. Bacillus suhtiUs: keep a bottle containing pond or creek water and a few algae tightly corked for 24 to 48 hours; a drop of the culture will show under the high power great numbers of short thread-like colorless plants moving about actively in the field; if they can not be observed readily, kill and stain them by adding a drop of gentian violet at the edge of the cover; draw several plants; 5. Account for the absence of chorophyll. Is there a distinct wall? Can you distinguish cytoplasm or nucleus? Are the cells all alike except for size? Is there anv trace of fission? Contrast the movement with that shown by Oscillatoria. Show what changes are necessary to derive Bacillus from Oscillatoria. (f. 62, p. 128.) 7. Bpirillum undula: in the above culture there will be found bacteria resembling Bacillus but exhibiting a spiral or snake-like motion ; draw several of these cells, paying especial attention to the turns of the spiral ; 5. Compare Spirillum and Bacillus. Docs the former always move with the same end forward? What does this indicate? Stain with gentian violet if necessary, (f. 62, p. 128.) structure and classification 59 branch f�hycof�hyta Class Chlorophycp:ae ORDER PROTOCOCCOIDBAE FAMILY PLEUROCOCCACEAE 8. Protococciis viridis: remove and mount a little of the green crust which grows on flower pots in greenhouses and upon the bark of trees ; a plenti- ful supply of the plant may be obtained by teas- ing apart the grey lichens which grow on trees; draw several single plants and also a cluster; 2. Is there a definite wall? Plastids? Note the different stages of fission. Compare with the same process in the blue green slimes. Are the cells in definite colonies or are they simply clustered? Compare Protococcus with Gloeo- capsa. (f. 66, p. 135 : IV, 11.) 9. Scetiedesmus ohliquus: draw several groups, show- ing the cells in 4's, 8's, etc. ; 2. Do the cells occur in definite colonies? Can you explain this grouping? Contrast the fission with that shown by Protococcus. Do the cells have pyrenoids? Are any of the cells pointed or spiny? Why? Do you find the protoplasm rounding up in any of the cells or escaping as a spherical moving cell, the zoogonid? Sometimes the latter are found swimming about in the mount in great numbers. ( f. 66, h, p. 135 : IV, 10.) FAMILY DESMIDIACEAE 10. Closterium lanceolatum: draw one cell, paying especial attention to the structure; each plant is 60 MANUAL OF BOTANY composed of two so-called half-cells, the separation of the two being indicated by a clear space in the center of the cell; at either end is a clear bubble or vacuole filled with tiny oblong bodies resembling bacteria in active motion; these are crystals of gypsum, calcium sulphate, which are to be regarded as waste products of the plant ; 1. Do vou find anv evidence that the wall is com- posed of two parts or valves? How many plas- tids are there? Do thev run the length of the plant? Do they lie against the wall or centrally in the cavity? Wliere are the pyrenoids? Con- trast a Closterium ^uth a Protococcus cell. Do the cells move? (f. 71, p. 139 : V, 1.) FAMILY BACHXASIACEAE 11. 'NavicuJa viridis: draw one live cell, showing the plastids and if possible a dead one showing the striations of the silicious wall ; 1. To what is the brown color due? move? Are there any pyrenoids? Do the cells Contrast the plant with Closterium. (f. 72, p, 140.) FAMILY ZYGXEMACEAE 12. Spirogyra nltida: draw a cell from a vegetative filament showing the details of structure ; f ; from filaments in conjugation, draw three groups of conjugating cells, the first showing the conjugating tubes forming and the plastids still intact, the second, the union of the conjugating tubes and the passage of the condensed protoplasm from one cell into the other, and the third the formation of the spore or zygote; J. ; STRUCTURE AND CLASSIFICATION 61 How many chloroplasts in the vegetative cell? Where are the pjrenoids? Is a nucleus present? Discuss fully the details of conjugation as gath- ered from the different filaments. Does the zygote have a thick wall? What is the purpose of the zygote? Compare Spirogyra with Clos- terium. (f. 73, p. 142,) FAMILY MUCORACEAE 13. Ascophora mucedo: examine without cover-glass under the low power a tuft of erect threads or hyphae bearing the black sporangia; draw such a tuft, and under the high powder a single stalk with its sporangium and spores ; 1. Why is the plant colorless? What effect has this habit had upon the cell partitions? How are the little tufts formed? How do the spores escape from the sporangium? Do you find any root-like structures? The reproduction is by conjugation it is, however, practically impossible to obtain it in the ordinary cultures, (fs. 74, p. 144; 75, p. 145; 76, p. 146: XIV, 4.) ORDER SIPHONEAE FAMILY VAUCHEBIACEAE 14. Yauclieria haniata: draw a portion of the main filament showing a lateral branch bearing oogones and antherids, also the zoosporangium if present ; 1. Is the main filament one-celled or many-celled? How is the zoospore formed? Describe the oogone and antherid in detail. Compare them 62 MANUAL OF BOTANY with the reproductive cells in Spirogyra. Do you find any chloroplasts, pvrenoids, or nuclei? (f. "^ 78, p. 150; XII, XIII.) FAMILY PEKOXOSPORACEAE 15. Peronospora parasitica: mount some of the mycelium in weak alcohol and draw one of the branched stalks or conidiophores with its conidia ; macerate a x^ortion of the leaf and draw an oogone and antherid; 1. Compare Peronosj^ora with Vaucheria. Explain the reduction of the plant body. TMiy does the plant have conidia instead of zoogonids? In what ways does it resemble Ascophora? (f. SO, p. 153, f. 85, p. 155; XVI, 21.) ORDER CONFERYOIDEAE FAMILY ULOTKICHIACEAE 16. Microspora ahhreviata: draw a filament showing the detail of the cells and the formation of gonidia ; 2. What are the chloroplasts like? How many in each cell? Do you find pyrenoids or a nucleus? How do the zoogonids arise? Do you find more than one kind? What is their function? What important differences between Microspora and Vaucheria? (f. 86 B, p. 157.) FAMILY OEDOGOJiTIACEAK 17. Oedogonium nodulosum: draw a filament showing the oogones and the dwarf males which bear the antheridia; 1. Describe the oogones and dwarf males in detail. STRUCTURE AND CLASSIFICATION G3 In what respects do these organs differ from those of Vaucheria? What is the oospore? How does it arise? Why should there be several an- therids for each oogone? Describe the structure of the vegetative cell. (f. 87, p. 159; f. 88, p. 160.) Class Phaeophyceae ORDER PHABOSPOREAB FAMILY ECTOCARPACEAE 18. Ectocarpus litoralis : draw a portion of a filament showing the branching and two or three stages in the development of the plurilocular sporan- gium; draw also a row of unilocular sporangia; 1. What is the color of the plant? What is it due to? Is chlorophyll present? Do you find pyrenoids or plastids? How do the plurilocular sporangia arise? The unilocular? How do their respective zoogonids differ? Compare Ectocar- pus with Microspora. ORDER FUCOIDEAE FAMILY FUCACEAE 19. FuGus fastigiatus: mount a thin transverse section of the fruiting tip and draw one of the pit- like conceptacles, paying especial attention to oogones, antherids, and sterile hairs, the paraphyses ; 1. How does the tissue of the tip differ from parenchyma? Why should the fruiting organ be ; 6i MANUAL OF BOTANY sunken in the tissue? What is the purpose of the paraphvses? Describe the antherids and oogones. Distinguish between isogametes and heterogametes. Illustrate, (f. 90, p. 164; f. 91, p. 165.) Class Rhodophyceae order florideae FAMTLT EHODOMELACEAE 20. Poli/sipJwnia fastigmta: draw a portion of the main stem bearing a tetrasporic branch; also a branch showing antherids and one with a cysto- carp; 1. Compare tetraspores with macrozoogonidia. What important differences between the cysto- carp and the oogone. Describe the plant body. To what is its color due? Why is this plant higher than Oedogonium or Fucus? (f. 95, p. 172.) Class Ascomycetes ORDER PERISPORIACEAE FAMILY ERYSIPHACEAE 21. TJncinula salicis: scrape a number of the spore fruits from the leaf of the host and mount in weak alcohol ; draw a perithecium under the low power with especial attention to the appendages crush the perithecium and draw the cluster of spore sacs or asci, with their spores ; 1. What kind of a plant is this? How does it STRUCTURE AND CLASSIFICATION 65 obtain its nourishment from the host? Do you find any vegetative filaments? Are there any differences between the perithecium, and the cystocarp of Polysiphonia? Upon what leaves do you find this fungus? Have you seen a similar fungus on any other plant? How can the spores escape from the perithecium? (f. 99, p. 176.) ORDER TUBERALES FAMILY TTJBERACEAE 22. Tuber melanosporum : cut a thin section of the spore fruit and draw three or four asci in posi- tion among the sterile threads; 1. Describe the spore fruit? Where is it found? Are any vegetative filaments present? What evidences of relationship between this plant and Uncinula? How do the spores escape? (f. 102, p. 180.) ORDER PYRENOMYCETALES FAMILY HYSTERIACEAE 23. HysterograpMum fraxini: cut a cross-section of the perithecium and make a diagrammatic drawing showing the position of the asci and paraphyses; also draw a single ascus with paraphyses and spores; 1. Describe the perithecium and its contents. How is this plant different from Uncinula? How do the spores escape? Where is the plant found? Is it a parasite or saprophyte? Why? (f. 104, p. 182.) 66 MANUAL OF BOTANY ORDER DISCOMYCETALES FAMILY PEZIZACEAE 24. Sepultaria scutellata: cut a cross-section of the spore fruit, the apothecium. and make a diagrammatic drawing showins: the position of asci and paraphTses; also draw one ascus with its spores and paraphyses; 1. Describe the structure of the apothecium. Con- trast this plant with Hvsterographium. Which do you think the higher? Why? How do the spores escape? How do thej differ from those of the preceding plant? Where is this plant found? Is it a parasite? Why? TMiat is the purpose of the spiny hairs on the outside? (fs. 106, 107, p. 185.) FAMILY PABMELIACFAE 25. Physcia stellaris : cut a cross-section of the apothe- cium throtigh the disk or hymenium and the vegetative body or thallus ; draw a segment extending from the hymenium through the thallus, paying especial attention to the asci and the Protococcus cells of the thallus; 1. Describe the apothecium and the thallus in detail. In what important respects does this plant differ from the preceding ascus-bearing plants? Is this union of Protococcus and fungus favor- able to the former? Why? Where is this plant found? How_ would you recognise a lichen? (f. 110, p. 187.) STRUCTURE AND CLASSIFICATION 67 ORDER UREDINALES FAMILY UREDINACEAE 26. Puccinia pliragmitis: the first stage of this plant appears in May or June upon the leaves and leaf- stalks of the ash ; the spores formed in the yellow cluster-cups fall upon the leaves of the cord grass where they germinate, producing finally one- celled summer spores; later the same vegetative filaments produce black two-celled winter spores draw a group of summer spores and winter spores; 1. Why are the winter spores thick-walled? Where is the wall the thickest? Why? Explain the thin walls of the summer spores. Do you find any resemblance between the winter spore and an ascus with spores? (f. 113, p. 192.) ORDER USTILAGINALES FAMILY USTILAGINACEAE 27. Ustilago maydis: this plant occurs in great masses of spores in swollen, "smutted" ears of corn, rarely, when the fungus is developing, in masses of filaments, which produce spores internally at the tips; draw a group of spores; 2. In what respects does this plant resemble Puccinia? (f. 115, p. 197.) 8 MAXTTAL OF BOTA>"T I^fcoper: :vfli: niake a dravii^ of fke puff-ten^ ivid^ :- riU^ tke i^ore fmit, and dianr also sane c:' -.l- ir^ads and spoies <tf the ]Bii!nor;2. fe ft a s.it:: :i"-"t ' i 11" " 1-r , 29- Agmriem.^ ;: i::�r ^ l::":i^ :f :ir en aw a w? ;.-'> (tiis, I : 1 CLi^^ CHAMQglffYClSAB WUellm opmem: dr:i . 7 : z : a pJant natural Hie, fliMmii^ lAe i 1 : : and liie nrandUn^; draw tte vpper part of 1 r^: ziTii^ Hie detail of the STRUCTURE AND CLASSIFICATION 69 cells and the archegone and antherid; crush the latter and draw a cluster of the antherozoidal filaments; 1. Describe the vegetative body in detail. Compare the archegone with the carpogone of Polysipho- nia and the oogone of Oedogonium. Why is it higher? What is the structure of the antherid? Where do the stoneworts grow? (f. 120, p. 205: XXVII.) branch bryof�hyta.. Class Hepaticae ORDER MARCHANTIALES FAMILY MARCHANTIACEAE 31. Marchantia polymorpha: draw a portion of the thallus, showing the brood cups and the taller antheridial and archegonial branches; cut a section through brood cup and thallus and draw in detail; make vertical sections of the antheridial and archegonial disks; note the structure and draw an antherid and an archegone; crush a mature spore-bearing plant or sporophyte and draw several spores and elaters; 1. Describe the structure of the thallus. Compare with it the wall of the brood-cup, and of the antheridial and archegonial disks. What does this show as to their origin? Contrast the stomata with those of flowering plants? What differences between the archegone and antherid of this plant and those of Nitella? What are the 70 MANUAL OF BOTANY elaters for? Distinguish critically between the sexual plant or gametophyte and the spore-bearing plant or sporophjte. (f. 121, p. 208; f. 122, p. 209; f. 123, p. 210.) Class Muscineae order bryales FAMILY PHYSCOMITRIACEAE 32. Funarla liygr^ometrica: draw a portion of the protonema, or young thread-like condition of the moss, showing the brown root-like filaments and the chlorophyll-bearing ones; draw the leafy plant, or gametophyte, bearing the fruiting plant, or sporophyte; draw the cluster of antherids and archegones, which usually occur sepa- rate at the tips of the gametophytes, along with the sterile threads or paraphyses; cut a longitudinal section of the capsule or sporophyte and draw the structure in detail. Contrast the gametophytes of Marchantia and Funaria. Contrast the sporophytes. What kinds of tissues in the moss? Where do the mosses grow? Why? (f. 125, p. 213; f. 126, p. 211; f. 127, p. 216.) Class Equisetineae order equisetales FAMILY EQUISETACEAE 33. Equisetum arvense: draw a gametophyte or prothallium, showing if possible the antherids and archegones ; make a drawing of the sterile and of STRUCTURE AND CLASSIFICATION 71 the fertile sporophyte, paying especial attention to the cone of the latter; draw also a portion of the cross-section of the cone, showing the shields and sporangia, and a spore showing the elaters. Describe the gametophyte and sporophyte in detail and compare them with the same structures among the Bryophyta. Where are the horse-tails found? Which appears first, the sterile or the fertile sporophyte? Which lasts the longer? (fs. 136, 137, p. 228.) Class Filicineae ORDER FILICALES FAMILY POLYPODIACEAE 34. Dryopteris marginata: carefully remove the earth from the lower side of a prothallium by thorough washing, and mount the latter lower side up; draw the prothallium with its rhizoids, antherids, archegones ; draw the leaf-like sporophyte, showing the fruit-dots or sori; draw a sporangium showing the spores. Compare the prothallium with that of Equisetum. Describe the sporophyte and compare it with the sporophyte of the Bryophyta. What tissues do you find in ferns? Are normal stomata present on the gametophyte? on the sporophyte? Where are ferns found for the most part? Which generation is usually termed ''fern," the gametophyte or the sporophyte? (f. 128, p. 220; f. 129, 130, p. 221; f. 133, p. 224.) 72 manual of botany Class Lycopodineae ORDER SELAGINELLALES FAMILY SELAGINELLACEAE 35. Selaginella rupestris: draw a portion of the plant showing the fruiting cones; make a longitudinal section of the cone and draw it showing the sporophylls, microsporangia and macrosporan- gia. Compare the sporophyte with that of the fern. What striking differences? What do these mean? Is the gametophyte present? What important differences from that of the fern? What differ- ences in structure and function between the macrospores and microspores? Where does this plant grow? (f. 139, p. 233.) Class Gymnospermae order coniferae FAMILY PINACEAE 36. Pinus austriaca: draw a cluster of the microspore cones (staminate cones), and draw from an axial longitudinal section of a cone, showing the microsporophylls, microsporangia, and the microspores (pollen grains) ; draw also a microspore; draw a macrospore cone (pistillate) and part of a section of it, showing macrosporophyll, placental scale, and macrosporangium. During the last half of May, a section of the macrosporangium will usually show also the macrospore STRUCTURE AND CLASSIFICATION 73 (embryo sac) which has already germinated to form a prothallium, which remains always enclosed within the spore ; at the tip of the prothal- lium (endosperm) may be found two or three elliptical hollows with necks, the archegones. Compare the pine tree, the sporophyte, with the sporophyte of Selaginella. What similarities and differences between the cones of the two plants? How does the prothallium of the pine differ from that of the fern? Contrast the relative size and importance of the gametophyte and sporophyte of the pine with the relative size and importance of the gametophyte and sporophyte of the liverwort, Marchantia. (fs. 141, 142, p. 240; f. 143, p. 241; f. 144, p. 243.) Class Angiospermae Subclass Monocotyledoneae ORDER CORONARIALES FAMILY LILIACEAE 37. Erythronium alhidum (Leucocrinum montanum, Tulipa gesneriana) : make a sketch of the whole sporophyte; make an accurate drawing of