ISOETACE^ 



S53 



leaves continues up to about the eighth, when the \ divergence 



is replaced successively by 



dition in the fully-developed sporophyte, 



\, I, I, tV and ix, which is the con- 



The Adult Sporophyte (Sadebeck (p) ) 



The structure of the mature sporophyte has been the sub- 

 ject of repeated investigations, among the most recent being 



Fig. 320. — ^A, B, Isoetes echinospora. A, Section of fully developed leaf, X15: B, 

 vascular bundle of the leaf, X about 200; C, part of a transverse section of the 

 stem of I, lacustris; sp, starch-bearing cortical cells; m, meristematic zone; h, 

 tracheids; hd, tissue of the 'central region (C after Potonie), 



those of Farmer (2) and Scott (2), who made a most careful 

 examination of the vegetative organs in I. lacustris and /. hys- 

 trix. The thick, very short stem has a central vascular bundle, 

 which as in the young plant is made up of the united leaf-traces, 

 and there is no strictly cauline portion, as Hegelmaier ( i ) and 



