XIV 



ISOETACEAi 



553 



leaves continues up to about tlie ci^htli, wlicn the l divergence 

 is replaced successively by \, |, -J, -^.^, and /i, wbich is the C(jn- 

 dition in the fully-developed sporophyte. 



Ttte Adttlt Sporoptiyte {Sodchcch (g)) 



The structure of the mature sporophyte has been the sub- 

 ject of repeated investij^'ations, anionj^- the UKjst recent ]m\v^ 



B. 



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

 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 /. lacustris and I. Jiys- 

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

 W'hich as in the young plant is made up of the united leaf-traces, 

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



