412 



VASCUI^AR CRYPTOGAMS. 



prolongation of the oosphere (probably a canal-cell, as in Ferns and Rhizocarps), 

 penetrates into the lower part of the neck. 



The Asexual Generation (Sporophore). The first divisions of the oospore are not 

 known ; but the mode of formation of the embryo differs, as may be concluded from 

 more advanced stages, from that of Ferns. Mettenius states that in Ophioglosswn 

 pedunculosum the end of the embryo which faces the apex of the prothallium 

 developes into the first leaf, while the opposite end produces the first root. Unlike 

 what occurs in Ferns, the concave upper side of the first leaf faces the neck of 



FIG. 288. — A Ophioglosstivi vulgaturn ; B Botrychiwn Lunaria (both natural size) ; iu roots, st stem, bs leaf-stalk, 

 X point where the leaf branches, the sterile lamina b separating from the fertile branchy: 



the archegonium ; the rudiment of the stem (which IVIettenius terms the * primary 

 rudiment of the embryo') lies nevertheless on the side of the embryo which faces the 

 base of the archegonium. Hofmeister, on the other hand, makes the following state- 

 ment with regard to Botrychium : — ' The position of the embryo with respect to the 

 prothallium differs widely from that which occurs in the Polypodiacese and Rhizo- 

 carpese ; Botrychium approaches in this respect those Vascular Cryptogams the 

 prothallium of which, like that of Ophioglossacese, is destitute of chlorophyll [Isoetes, 

 Selaginella). The punctum vegetationis of the embryo lies near the apical point of 



