CHAPTER XXI 



BRYOPHYTES 



The Bryophytes, comprising the two groups, hverworts (Hepa- 

 ticae) and mosses {Musci), present a great diversity of structure, some 

 being so dehcate that good preparations are very uncertain, while 

 others are so hard that it is difficult to get satisfactory sections. Be- 

 tween these extremes, however, there are many forms which readily 

 yield beautiful and instructive preparations. 



If but one fixing agent should be suggested for the entire group, it 

 would be chromo-acetic acid with 1 g. chromic acid and 2 c.c. acetic 

 acid to 100 c.c. of water. Wherever nuclear detail is desirable, particu- 

 larly in fertilization and the reduction of chromosomes, the addition 

 of 6 or 7 c.c. of 1 per cent osmic acid to this solution will improve both 

 the fixing and the staining. Fix for at least 24 hours : 48 hours may 

 be an optimum, but material, which has been in this solution for 

 3 or 4 days, still gives good results. Since this fixing agent is not 

 a good preservative, nothing should be left in it for more than 4 or 

 5 days. 



Professor Land used a formalin alcohol solution (6 c.c. commercial 

 formalin to 100 c.c. of 50 per cent alcohol) which he had tested in ex- 

 tensive collections in tropical Mexico and in various islands of the 

 South Seas, where it was impracticable to use the chromic series, with 

 its tedious washing and changing of alcohols. Material may be left in 

 this solution until needed for use, a convenience which will hardly be 

 appreciated by those who are always within reach of a laboratory. 

 Material left for more than 20 years in this solution, in well sealed con- 

 tainers, when opened recently, was found to be in excellent condition 

 for paraffin sections. Professor Land, in his more recent work, adds 

 some acetic acid to his original mixture. His formula, wdth various 

 modifications, is now the most generally used fixing agent for tropical 

 work and is widely used, even when the chromic series is practicable. 



For general study, the small, delicate forms, like Cephalozia, Fos- 

 somhronia, and Geocahjx, may be stained in eosin and mounted whole 

 in Venetian turpentine. 



Instead of treating forms in a taxonomic sequence, we shall consider 



274 



