Fig. 20 



Botrychium: a, B. lunaria; b, fertile pinnule; c, vascular supply 

 to sporangia; d, prothallus of B. virginianum; e, archegonium; 

 F, embryo of B. obliquum. Ophioglossum: g, O. vulgatum; h, 

 portion of fertile spike; i, vascular supply to sporangia; J, 

 prothallus of O. vulgatum; k, archegonium of O. pendulum; 

 L, embryo of O. vulgatum 



(f, foot; 1, leaf; r, root; s, suspensor; x, stem apex) 



(a, g, after Luerssen; b, h, Bitter; c, Goebel; d, k, Campbell; 

 E, Jeffrey; F, Lyon; J, l, Bruchmann) 



Ophioglossum varies considerably in its internal anatomy, 

 according to species. Some possess an outer endodermis, 

 but in most species it is absent, even in the young stages. The 

 leaf gaps in the xylem overlap one another, giving rise to a 

 network of meristeles, which form a rudimentary kind of 

 dictyostele. 



The xylem is endarch in Botrychium and Ophioglossum, 

 but mesarch in Helminthostachys. The earliest formed proto- 

 xylem tracheids are very similar to those of the Marattiales ; 



137 



