MOSSES AND FERNS 



CHAP. 



the archegonium is quite free at the base, and like that of 

 Aneura the wall of the venter is two -layered. The neck 

 becomes very long, and, according to Janczewski, the number of 

 neck canal cells may reach sixteen or even eighteen. 



The antheridia of Pellia are larger than in Aneura, but in 

 their development are similar except that the stalk is multi- 

 cellular. The spermatozoids 

 are the largest known among 

 the Hepaticai (Fig. 35, D, E). 

 In some species of Palla- 

 vicinia the very strongly de- 

 veloped midrib is made up 

 in part of thick-walled elon- 

 gated cells, but usually such 

 cells are absent. The develop- 

 ment of the sporogonium 

 is best known in Pellia epi- 

 phylla} Here the first wall, 

 as in Aneura, separates a 

 lower cell, which simply forms 

 an appendage, from the upper 

 cell, from which the stalk and 

 capsule develop. In the 

 latter the first wall is vertical, 

 and is followed in each of 

 the resulting cells by hori- 

 zontal walls, by which the 

 separation of the capsule from 

 the seta is effected. These 

 four cells are now divided 

 by vertical walls, so that two 

 layers of four cells each are 

 present. The first periclinal 

 walls in the apical group of cells separate the archesporium 

 from the wall of the capsule. 



The differentiation of the capsule and seta follows as in 

 A^ieura, and the arrangement of the cells of the archesporium is 

 much the same except that the rows of cells radiate from the 

 base of the capsule and not from the summit. The foot is 

 very distinct and forms a pointed conical cap, whose edges 

 1 Kienitz-Gerloff(i); Hofmeister (i). 



Fig. 40. — A, Young plant of Aneura palmata 

 (Nees), X 265 (after Leitgeb) ; B, three views of a 

 young plant oi Pellia calycina, X420 (Leitgeb). 



