PTERIDOPHYTES—FILICALES 
267 
like that shown in Figure 92 may be reached. At the end of a week, 
there may be green sporophyte more than a centimeter in length. 
It is obvious that material should be fixed at frequent intervals 
if one is to secure a series of stages in the development of the gameto- 
phytes and embryo. 
For sections showing the development of the antheridium and 
sperms, it is better to remove the megaspores from the sorus, since 
they occasion considerable difficulty in cutting. Fix in the special 
chromo-acetic-osmic-acid solution, cut 5 /jl thick, and stain in iron- 
alum haematoxylin. 
Fig. 92 .—Marsilia quadrifolia: upper portion of megaspore with an archegonium containing 
a young embryo. X212. 
The older megaspores, with the archegonium or embryos at the 
apex, are very hard to cut. Fix in hot alcoholic corrosive sublimate- 
acetic, or in alcohol-formalin-acetic acid. It will facilitate infiltration 
and cutting it you prick each megaspore with a sharp needle before 
fixing. Since the archegonium is at the apex of the megaspore, 
the pricking need do no damage. If sections come loose from the 
slide, use Land’s fixative. Cut 5 to 10 ju thick and stain in safranin, 
gentian-violet, orange. 
The sperm, which in Marsilia has an unusually large number 
of turns in the spiral, is easily mounted whole. When the sperms 
have become numerous, put several megaspores upon a slide and 
heat gently until dry. Then wet the preparation in any alcohol and 
stain sharply in acid fuchsin. Dehydrate in absolute alcohol for 
