LABOTUTOnr STUDIES OF CliYl'TOGAMS 157 



XV. LABORATORY STUDIES OP CRYPTOGAMS 



[Note : — Many of the following types may be studied \Yitliout 

 compound microscopes, if good hand lenses or, better, dissecting 

 microscopes, are provided. In tlie suggestions for study wliicli fol- 

 low, (simple) following the number of a paragrapli indicates that tlie 

 simple microscope is to be used; similarly, (couipoiuid) indicates that 

 a conipiound microscope is to be used ; and (compound or simple) 

 indicates that the simple microscope may be used, but the compound 

 is to be used if available. ] 



346 (Compound). Nostoc. Make a note of the general character 

 — form, consistency, color, etc. — of the masses in which the plant 

 occurs. Mount a bit of tlie mass in a drop of water on a glass slide, 

 cover with a cover glass, pressing the latter down gently, and examine 

 first with a low, then with a higher power of the compiound mioio- 

 scope. 



What constitutes one single individual plant? How are the indi- 

 viduals grouped? Wliat is the color? Are any cells distingidslied 

 by size or other character? What holds the cells and chains (colonies) 

 together? Draw one chain by aid of the highest p)0\ver yon have. 



347 (Compound). Unicellular Green AlgcE : Pleurococcus, or the 

 like. Upon what do the plants provided grow? Examine this sub- 

 stratum with the hand lens, to see if the individual plants causing the 

 green tinge on the surface can be distinguished. Then scrape a bit 

 of the green film into a drop of water on a glass slide, cover, and 

 examine with different powers of the compound microscope, the lowest 

 first. Do you find the plants single? In groups? If in both ways, 

 draw both. Is there anything in the number of plants in a group, or 

 in the position of the members of a group, or any other circumstance, 

 to suggest to you the way in which these plants multiply? 



348 (Simple). Spirogyra. Use the simple lens to obtain an idea 

 of the actual size of the plants. Do the filaments branch? Are there 

 cross partitions? Do any parts of the filaments differ markedly from 

 others ? IIow does the color differ from tliat of Nostoc, if at all ? 

 What portion of any cell bears the color? What is the arrangement 

 of the color-bearing bands (chromnlophoret^') f 



349 (Compound). Is there more than one chromatophore in each 

 cell ? Draw a short portion of one filament, using a moderate power. 

 Indicate, without drawing all of them, the arrangement of the chro- 

 matophores. 



350 (Compound). Select a cell (for example a terminal cell) in 

 which the spirals are rather loo.se. Look for the nucleus, near the 

 center, a colorless body from which colorless strings radiate. If this 

 jsnot distinguishable, delay search until after the following treatment. 



