xxxix] 



ONYCHIUM 



^7 



is interrupted : occasionally the series of cells may be doubled (Fig. 627). 

 Such instability of structure is held to be an indication of a primitive state, 

 since it occurs in sporangia that are short-stalked and pear-shaped, and the 

 variants point towards an uninterrupted oblique annulus, such as is actually 

 present in Plagiogyria, and the more complex stalk characteristic of relatively 

 primitive Ferns. Spore-countings give numbers varying from 45 to 52. 



Fig. 625. Cjyptograinme crispa R. Br. .-/ = part of a strong plant, with one fertile and two sterile 

 leaves, \ natural size. ^ = segment of the second order with inrolled margins still covering the sori ( x 4). 

 C = part of a segment of the third order, enlarged : the left flap reflexed to expose the sori : those of 

 the uppermost nerve-fork have been removed. (After Luerssen.) 



Fig. 626. Ciyptogranutie (AUosoriis) 

 crispa (L.) R. Br. Tip of a sporo- 

 phyll-segment, seen from below. 

 The sporangia are shaded. Magni- 

 fied. (After Von Goebel.) 



Onychium Kaulf 



Onychimn, which also bears its sporangia upon the vein-endings, was 



separated as a distinct genus by Kaulfuss, and it is maintained as such in 



Christensen's Index, though it was included in Cryptogramme by Prantl 



(634, p. 413). The difference lies in the fact that the veins which bear the 



5-2 



