shoot, and finally almost completely disappear, so that the oldest pan of 

 the shoot is almost pcrfe idrical. The surface of the wings is 



smooth and the margin undulate, but not developing lobes or teeth, in this 

 respect differing from P. Zolli*K< 



The ice of the midrib is completely covered by short 



papillate hairs, like the true rhiioids. outgrowths of single superncial cdls. 

 These papillae become longer in the older parts of the thallus. and 

 gradually give place to the long, dark purple-red rhiioids. which in the 

 basal region form a dense mast. These conspicuous rhiioids (Fig. 7. 

 D, E) are composed of a single cell, but develop a number of short 

 brant: Z oiling fri ventral, apparently adven- 



u branches are developed which much resemble the main shoots, but 

 arc somewhat smaller. It is highly propable. however, that under favor- 

 able circumstances these develop into perfectly normal plants. Their 

 origin was not investigated, but it is probable that they arise in much the 

 same way as the similar branches in P. ZoUin, 



Q\ ucnt ly the wings of the thallus are attenuated anteriorly 



as well as posteriorly, and as a result the apex of the shoot is somewhat 

 pointed. In form and size the male and female plants are very similar 



The anthcridia form a row on each side of the midrib, and are 

 arranged in elongated groups separated by sterile areas ( Fig. ; 

 They arc attached to the side of the midrib and project laterally, but are 



ted slightly forward. They are covered by broad scales, one cell in 

 thickness, which arise at intervals behind an antheridium and, pasting 

 above it, extend along the side of the midrib at a shelf-like projection. 



e scales are deeply incised, scalloped, and sometimes toothed, vary- 

 ing much in size and shape. The scales may subtend a single antheridium 

 or a small group. Sometimes no antheridium is formed under a scale 

 7, C). The anther acropctal succession, and 



the -calt -x near the apex cover immature anthcridia only. 



.ile plants (Fig. 8. E) closely resemble the males, except for 

 the different appearance of the reproductive organs. The archegonial 

 receptacles resemble those of P. Zoll. ut are much larger. 



They arise at various points upon the dorsal surface of the midrib, but 

 there is no connection between their formation and the branching of the 

 thallus. They possess the conspicuous perianth and involucre character- 

 ic other members of the genus. The archegonia are much more 

 numerous than in either of the other species examined. The involucre, 

 also, is more conspicuous, having a deeply incised spreading margin. 

 which is strongly revolutc. 



