V 1 1 [ 



THE FTERIDOPHYTA—OPHIOGLOSSA CE^ 



251 



sions take place in all directions until a very larijc numbcr 

 of cells is formed. The cells immediately adjoinini^ the 

 sporogenous tissue divide into tabular tapetal cells, as in 

 OpJiioglossum. The sporangium shortly before the isolation 

 of the spore mother cells (F'ig. 129, C) is a nearly globular 

 body with a thick, very short stalk. The central part of the 

 upper portion is occupied by the sporogenous tissue sur- 

 rounded by a massive wall of several layers of cells, of which 

 the inner ones constitute the tapetum. The central cells, as 



Fig. 129. — Botrychiutn Virgininmtin (Sw.). Development of the sporangia. A, i, 2, Very young 

 sporangia ; B, a som what older one, X 480 ; C, older sporangium, X 240, all median longitudinal 

 sections, the sporogenous cells have the nuclei shown. 



usual, have larger nuclei, and more granular contents than the 

 outer ones. The stages between this and the ripe sporangium 

 were not seen, so that it cannot be stated positively whether all 

 the cells of the sporogenous tissue (which seems probable) or 

 only a part of them, as in OpJiioglossum, develop spores. 



The stalk is traversed by a short vascular bundle, which is 

 first evident about the time that the number of sporogenous 

 cells is complete, and joins directly with the young vascular 

 bundle of the leaf segment (Fig. i 29, C). The ripe sporangium 

 opens by a transverse slit, as in Opiiioglossuin. 



