242 
METHODS IN PLANT HISTOLOGY 
an extensive study of Spagnum subsecundum , found that antheridia 
appear in August and archegonia in September. In examining acres 
of this species, he did not find a sterile plant. 1 
Sporophyte.—It is often difficult to get good mounts of sporo- 
phytes. In the younger stages the calyptras are likely to interfere 
Fig. 76—Mnium: upper part of capsule showing two teeth of the peristome cut longitudinally; 
a, annulus. Fixed in formalin alcohol and stained in safranin and light green. X120. 
with cutting, while in the older stages the peristome, or hard wall 
of the capsule, occasions the trouble. If an attempt is made to 
remove the calyptra in young stages, like A of Figure 74, the apex 
of the sporophyte usually comes with it. While picro-acetic acid 
material cuts more easily, chromo-acetic acid followed by Dela- 
field’s haematoxylin gives so much sharper differentiation in stages 
1 Botanical Gazette, 59 :40-56, 1915. 
