IO 



GENUS PALLAVICINIA 



by Farmer [i]. In this species the form of the apical cell is quite differ- 

 ent from that of P. Zollingeri, It has the form of a three-sided prism. 

 Four sets of segments are formed, three lateral and one basal, instead 

 of the two sets of lateral segments found in P. Zollingeri. 



Long, slender, simple rhizoids which are developed from the super- 

 ficial cells, are formed in great numbers upon the prostrate rhizomes. 

 Here and there occur isolated scales, one cell in thickness, and very much 

 like those which cover the antheridia. 



Pallavicinia Zollingeri. 



A. Segment of the frond of an antheridial plant, x 25 (about). 



B. A portion of A, more highly magnified. 



C. Longitudinal section of the shoot, passing through an antheridium, and showing 



the strand of conducting tissue. 



D. Cross-section of a segment of the frond, showing the position of the antheridia 



on the dorsal surface of the midrib. 



