MOSS DEVELOPMENT. 13 
always much smaller than that of the leaves; they are in many 
cases definitely limited in their growth, and lead to the formation 
of ramified systems, similar to pinnate leaves, as in Thuidium and 
Hylocomium. 
The origin of the lateral shoots has been carefully investigated 
by Leitgeb in the case of Fontinalis and Sphagnum, and the results 
obtained are of general application to the whole class, since these 
two genera belong to very different sections. 
They agree in the fact that the apical cell, or mother-cell, of a’ 
branch originates beneath a leaf from the same segment as the 
leaf. In Fontinalis the branch arises beneath the median line of 
the leaf; but in Sphagnum, in consequence of the further develop- 
ment of the mother shoot, the lateral shoot appears at a later 
period to stand by the margin of an older leaf; articulated hairs 
arise in the axils of the leaves of Fontinalis and Sphagnum. 
The dimensions attained by the leaf bearing axes of Mosses 
show a wide range, the simple stem in Phascaceze, Buxbaumia, 
and others, scarcely reaching one-twentieth of an inch in height, 
while the largest species of Hypnum and Polytrichum range from 
6 to 12 inches, and more. 
The thickness of the stem is less variable, being ;4, inch in the 
smallest, and hardly exceeding 4; inch in the thickest forms. 
Its dense tissue is, however very firm, often stiff, very elastic, 
and capable of offering long resistance to decay. 
The Root-hairs (Rhizoids) play an extremely important part in 
