268 



MOSSES- AND FERNS 



CHAP. 



Strongly than the other, so that the latter appears lateral. 

 With the assumption of the pinnate form the leaf also develops 

 the wings or appendages upon the axis between the pinnae. 

 In the fully-developed leaves of the mature sporophyte, the last 

 trace of this is seen in the ultimate branching of the veins, 

 which is always dichotomous. 



The second root arises close to the base of the second leaf, 

 and at first there seems to be one root formed at the base of 

 each of the young leaves ; in the older sporophyte the roots are 

 more numerous. Holle ^ states that this is not the case in 

 Marattia, where only one root is formed for each leaf, in 

 Angiopteris two. This, however, requires confirmation in the 

 older plants. As the roots become larger it is no longer 



Fig. 140. — A, Longitudinal section ; B, transverse section of roots from older sporophyte of 

 M. Douglasii, showing apparently more than one initial cell, X 200. 



possible to distinguish certainly a single initial cell. The 



adjacent segments themselves assume to some extent the 



function of initials, and thus in place of the single definite 



apical cell a group of apparently similar initials is formed, which 



takes its place (Fig. 140). This seems to be in some degree 



associated with the increase in size of the roots.^ 



According to Holle ^ the four-sided apical cell found in the 



stem of the young sporophyte is retained permanently, but in 



Angiopteris this is not the case, as in the older sporophyte a 



single apical cell is not certainly to be made out. Bower ^ 



1 Holle (2), p. 217. 



^ It is possible that a single initial may be present even here, but the great similarity 

 of the central group of cells makes this exceedingly difficult to determine. 

 3 Holle, I.e. p. 218. * Bower (ii), p. 324. 



