286 METHODS IN PLANT HISTOLOGY 



with your finger. Nearly all of the soil will soon be removed. Put it in 

 a bottle of water and shake. Pour it out into a flat dish and transfer 

 the protonema to clean water. If there is still some soil, pat it with 

 your finger. In this way you can soon clean enough for a thousand 

 mounts. 



Permanent mounts are very easily made. Simply wash away the 

 dirt with water and put the material into 50 per cent glycerin, and let 

 the glycerin concentrate. Mount in glycerin or glycerin jelly for per- 

 manent mounts. Seal thoroughly. Such mounts, with no fixing or 

 staining, may retain the green color for many years. 



If you do not insist upon keeping the green color, much clearer 

 mounts can be made by fixing in formalin acetic acid, about 10 c.c. of 

 formalin and 5 c.c. of acetic acid to 100 c.c. of water, and staining in 

 eosin or in phloxine and anilin blue. A good stain in Delafield's haema- 

 toxylin gives a beautiful purple color and is permanent. Mount in 

 Venetian turpentine. 



Antheridia. — It is easy to find material for a study of antheridia, 

 because, in so many cases, the antheridial plants can be detected at 

 once without even a pocket lens. Funaria, with its bunch of anther- 

 idia as large as a pinhead, is extremely common everywhere. Spring 

 is the best time to, collect it, but it is found fruiting in the autumn and 

 sometimes in summer; besides, it is easily kept in the greenhouse, 

 where it may fruit at any time. Br yum roseum has a large cluster of 

 antheridia surrounded by radiating leaves, making it easy to recog- 

 nize. Other species of Bryuni and species of Mnium, hke M. cuspi- 

 datum, make good sections. Polytrichum has a large cluster of anther- 

 idia surrounded by reddish leaves, so that the whole is sometimes called 

 the moss "flower." In fixing this or the closely related Atrichum {Ca- 

 tharinea), cut a small slab from two sides, so as to leave a flat piece to 

 cut for longitudinal sections. This trimming will greatly facihtate fix- 

 ing and infiltration. A single antheridial plant of Polytrichum often 

 furnishes a fairly complete series of stages in the development of 

 antheridia. Transverse sections show not only the antheridia but also 

 good views of the peculiar leaf of this genus. In all cases the stem 

 should be cut off close up to the antheridia, for many of the moss 

 stems, after they have begun to change color, cut like wire. 



Sections to show the development of the antheridium should be 5 to 

 10 ju in thickness. The safranin, gentian violet, orange, is a good com- 

 bination (Fig. 85 A). For details of spermatogenesis, sections should 



