BRYOPHYTES— HEPATICAE 



281 



Riccia natans into paraffin without shrinking, and the same thing may 

 be said of other forms which have such loose tissue with large air 



Fig. 81. — Riccia natans: A, habit sketch showing four rows of sporophytes. X2. B, nearly 

 mature antheridium. X345. C, nearly mature archegonium, with egg, ventral canal cell, and 4 neck 

 canal cells. X720. D, young sporophyte inclosed in the swollen archegonium: the inner cells (endo- 

 thecium) shaded; the outer layer (amphithecium) only onelayer of cells thick, lightly shaded. X200. 

 E, nearly mature sporophyte, inclosed by the greatly swollen venter of the archegonium. The 

 broken-down amphithecium represented only by a line. Spores in tetrads. X 100. From Chamber- 

 lain's Elements of Plant Science (McGraw-Hill Book Co., New York). 



cavities. Formerly, we resorted to celloidin for stages like that shown 

 in Figure 81. The gradual processes already described have obviated 

 the difficulty, so that the student should be able to get thin paraffin 



