XIV 



ISOETACEJE 



553 



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

 is replaced successively by ^, |, |, ^%, and /t, which is the con- 

 dition in the fully-developed sporophyte. 



The Adult Sporophyte {Sadebeck (p)) 



The structure of the mature sporophyte has been the sub- 

 ject of repeated investigations, among the most recent being 



B. 



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 /, 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 7. lacustris and 7. 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 



