634 Journal of Applied Microscopy. 



METHODS IN PLANT HISTOLOGY. 



Charles J. Chamberlain. 



X. 

 BRYOPHYTA. 



The Bryophytes, comprising the two groups, Liverworts (Hepaticae) and 

 Mosses (Musci), present a great diversity of structure, some being so delicate 

 that good preparations are very uncertain, while others are so hard that it is 

 difficult to get satisfactory sections. Between 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 three-quarters g. chromic acid and one-half cc. acetic acid 

 to 100 cc. of water. It should be allowed to act for at least twenty-four hours, 

 and perhaps two or three days is better. Always make an effort to get the 

 material into paraffin, using celloidin only as a last resort for refractory structures 

 which resist infiltration and for very delicate structures which persist in collapsing. 

 As one gains in experience and carefulness, the number of cases which seem to 

 demand celloidin will become fewer and fewer. 



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

 gametophyte structures under the headings tha/lus, antheridia, and archegonia, 

 and shall then turn our attention to the sporophyte. 



HEPATICAE. 



Some of the liverworts are floating aquatics, but most of them grow on logs 

 or rocks or upon damp ground. They are found at their best in damp, shady 

 places. Many of them may be kept indefinitely in the greenhouse. Riccia, 

 Ricciocarpus, Marchantia, Conocep/ialus, Asterella, and many others vegetate 

 luxuriously and often fruit if kept on moist soil in a shady part of the green- 

 house, and they do fairly well in the ordinary laboratory if covered with glass 

 and protected from too intense light. The living plants are very desirable, since 

 they not only furnish the best possible material for habit work and the coarser 

 microscopic study, but they also enable one to secure complete series in the 

 development of the various organs. 



The tJiaUus. — In many cases 'it will not be necessary to make a special 

 preparation for the study of the thallus, since preparations of antheridia, arche- 

 gonia, or sporophytes may include good sections of vegetative portions. This is 

 particularly true of forms like Riccia, where the various organs are not raised 

 above the thallus. In forms like Marchantia, where the antheridia, archegonia, 

 and sporophytes are borne upon stalked receptacles, it is better to make separate 

 preparations to show the structure of the mature thallus. Sections intended to 

 show the structure of the mature thallus should be 15 /< to 25 /< in thickness, but 

 sections to show the growing point and development of the thallus should not be 

 thicker than 10//. Material showing apical cells and development of the thallus 



