THE HOMOSPOROUS LEPTOSPORANGIATJE 



363 



subject of numerous investigations, but there still is a good 

 deal of diversity of opinion as to their exact method of growth. 

 Bower ( (n), p. 310) states that in O. regalis there may be a 

 single apical cell, such as exists in the first root of O. Claytoni- 

 ana and O. cinnamomea, but that it never shows the regular 

 segmentation of the typical leptosporangiate root, and it may 

 be replaced by two or three similar initials. In Todea barbara 

 he found four similar initials, and in no case a single one, 

 although Van Tieghem and Douliot ((5), p. 378) ascribe to 

 this species a single three-sided apical cell. 1 



f 



FIG. 205. A, Longitudinal section through the root apex of O. cinnamomea; t, young 

 tracheids, X,2oo; B, cross-section of root apex of O. Claytoniana, Xaoo. 



Osmunda cinnamomea (Fig. 205, A) shows a single very 

 large initial, more or less triangular in form when seen in pro- 

 file, but with the point sometimes truncate. Transverse sec- 

 tions show that it is really a four-sided pyramid. The young 

 segments are very large, and it is possible that these may some- 

 times assume the role of initials. Owing to the slowness and 

 irregularity of cell division it is difficult to trace the limits of 

 the segments beyond the youngest ones. They usually form 



1 Lachmann ( i ) asserts, however, that he found a group of initials such 

 as Bower describes. 



