IX 



jlIA RA TTIA CEAC—ISOE TA CE^ 



281 



wanting, and the first transverse wall separates the central cell 

 from the cover cell. The first division in the inner cell is 



Fig. 147. — Isoetes echinospora var. Brauiiii (Dur.). A, Longitudinal section through the apex of 

 the female prothallium, showing the first cell formation, x 300 ; B, similar section of a prothallium 

 with the divisions completed and the first archegonium (ar) already opened. 



parallel with the base of the cover cell, and divides it into the 

 primary canal cell and central cell. The contents of the three 



