412 
VASCULAR 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 Ophioglossum 
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 Ophwglossicni vulgntitm ; B Rotrychium Lunaria (both natural size) ; w roots, stem, bs leaf-stalk, 
X point where the leaf branches, the sterile lamina b separating from the fertile branch ß 
the archegonium ; the rudiment of the stem (which Mettenius 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 
