MUSCI 137 



leafy stems appear never or very seldom to arise at the apex of a primary 

 filament of the protoneme, but always as lateral branches. 



Mosses display a certain amount of differentiation of tissues. The 

 apical cell of the stem is, except in Fissidens (Hedw.), a three-sided 



Fig. zoz.—Catkarinea (^Atrichum) nndttlaia W. and M. (magnified). (After Schimper.) 



pyramid. The prirnary meristem of the stem, situated beneath the 

 growing point, which develops into the permanent tissue, usually becomes 

 differentiated into an inner aftd a peripheral mass.; the latter, although 



