FILICINE^ LEPTOSPORANGIAT^ 



309 



include a triangular cell, which is the " two-sided " apical cell of 

 the next phase of the prothallium's growth. The divisions up 



Fig. 156. — Onoclea stnithioptcris (Hoffm). A, B, Germinating spores with the perinium removed, 

 X 300 ; C, young prothallium, x 100 ; D, E, older prothallia with two-sided apical cell {x), X 300 ; F, 

 small female prothallium seen from below, X25; G, very young prothallium with the two outer 

 spore-coats, X 300 ; r, primary rhizoid ; ar, archegonia ; p, perinium ; ex, exospore. 



to this point correspond exactly with those of Aneura or 

 Metzgeria, and are also much the same as in Marattia, except 



