METHOD* 19 



measure only about 2 cm. in length and 4-5 n 1th The female 



plants (Fig. 9, B) are about 10 cm. in length and 7 mm. wide. 



The wings of the thallus are relatively v . and as usual but 



one cell thick. They are waved slightly on the margin, which is entire 



>t for an occasional cell w! ecu slightly to at to form an incon- 



>us tooth. Anteriorly the lamina of the antheridial plant narrows 



aru|t!> t . the apex of the shoot, which it indented. The midrib projects 



^ly on the v. !e The rhizoids are much less numerous than 



in P .IK! <|uite -liiTrrefit in color, being a rather light brown. 



instead of the deep purple- red found in P. radituloso. The conducting 

 strand of the midrib is much like that of /'. radifulota. 



v> "i the midrib in the male plant extend a series of 

 scales \\! a more or less continuous shelf-like structure. These 



scales have their free margins deeply lobed and toothed, and 

 the shelf formed by these confluent scales the anther 

 Mildly "r in Croups of several together < Kig. 9, A). The antheridii 



opetal succession, and are arranged in a somewhat broken row along 

 each side of Hie midrib They are more completely covered by the sub- 

 tending scales than is the case in P. rad\c*losa, and are not so evidently 

 roups separated by sterile areas. 



The antheridia, to judge from a somewhat cursory examination, 

 appear to agree in all essential details of structure with those of P. 

 culosa, 



The apical cell of the thallus is not so deeply placed as in P. 

 losa. but a study of horizontal and vertical sections shows that it has the 

 same form. On the ventral surface of the midrib in P. Levitri. as in P. 

 radicvlosa. there may occasionally be found small groups of meristematc 

 cells, which appear dormant, and do not show a definite apical cell The 

 smaller groups are slightly sunken; the larger ones, perhaps having 

 resumed activity, form hemispherical protuberances. The origin and 

 development of these groups of cells is apparently the same as the similar 

 ones in P. Zollingeri. and probably under favorable conditions these give 

 rise to normal branches. 



The archegonial plants of P. Ltvirri ( Fig. 9, B). besides being much 

 larger than the male plants, show also a very different appearance at the 



.>f the shoot. There is no indentation at this point, but the thai 



prolonged ino a nearly cylindrical process of some length, in which the 



wings are quite suppressed. It is possible that an examination of a larger 



number of individuals might show that this difference in apices of the 



female plants is not constant. The rhizoids of the female plants 



