BRYOPHYTES— HEPATICAE 



283 



figures during the first three divisions in these spores are exceptionally 

 beautiful and are very easy to stain with the safranin, gentian violet, 

 orange combination, the chromosomes taking a very brilliant red, while 

 the asters take the violet. Achromatic structures are very prominent 

 during these three divisions, but 

 become less and less conspicuous 

 as division progresses; and before 

 the intrasporal stage is over, the 

 radiations are scarcely demon- 

 strable. 



For the older sporophytes of 

 Marchantia, it is better not to cut 

 the whole receptacle. Remove the 

 radiating branches. The sporo- 

 phytes are in radiating rows, alter- 

 nating with the branches. A piece 

 2 mm. wide can be cut so as to in- 

 clude two of the radiating rows, 

 one on each side of the stalk, and 

 such a piece will include early 

 stages in other rows. By taking 

 such care, you can get median 

 longitudinal sections of nearly all 

 the sporophytes. For class work, 

 5 to 10 ^t is a good thickness, but 

 for figures, especially the reduction mitoses in the spore mother-cells, 

 the sections should not be thicker than 1 or 2 /z. 



Among the Bryophytes no form affords a better opportunity for 

 studying the development of spores than Anthoceros, since a single 

 longitudinal section of the sporophyte may show all stages, from 

 earliest archesporium to mature spores (Fig. 84). The sporophyte is 

 even more difficult to orient than that of Riccia natans. Cut a slice 1 

 or 2 mm. thick, so as to orient the visible portion of the sporophyte, 

 and trust to luck for the orientation of the foot. The starch grains in 

 the chloroplasts take a beautiful violet color with the safranin, gentian 

 violet, orange combination. With so many stages in a single section, 

 it will be impossible to stain all of them well. A stain which will show 

 the mother-cells and their divisions will be too deep for the mature 



Fig. 83. — Pfllin, epiphylln: photomicro- 

 graph of spore germinating while still within 

 the capsule. Fixed in chromo-acetic-osmic 

 acid, and .stained in safranin, gentian violet, 

 orange. Negative by Miss Ethel Thomas. 

 X276. 



