12 



GENUS PALLAVICINIA 



fronds are about 2.5 cm. in width (Fig. 5). In the male plants they are 

 somewhat smaller. The apex of each segment is indented, and the mar- 

 gin is wavy, with conspicuous teeth, or narrow lobes, which are usually 

 pointed and hooked (Fig. 4, A). 



A. Median section of an archegonial receptacle ; 



B. A nearly mature archegonium. 



C. D. Ventral part of two old archegonia. 



E. Receptacle containing an embryo ; cal. calyptra 



F. Transverse section of a similar receptacle. 



G. H. Archegonial receptacles. 



Pallavicinia Zollingeri. 



in, involucre ; per, perianth. 



