76 



MOSSES AND FERNS 



CHAP. 



surface of the plant, they give it a most characteristic 

 appearance. Usually each archegonium has its own envelope, 

 but Leitgeb ^ states that two or even more may be surrounded 

 by a common envelope. When ripe, the venter of the arche- 

 gonium is somewhat enlarged, but not so much as in Riccia. 

 The egg-cell is very large, oval in form, and nearly fills the 

 cavity of the single-layered venter. 



The first wall in the embryo is transverse, and divides the 

 egg cell, which before division becomes decidedly elongated, 

 into two nearly equal cells. Ordinarily in each of these cells 



Fig. 29. — Sphcerocarpus ter7-cstris var. Californicus (Aust.). Development of the archegonium. 

 A-C, Longitudinal sections, x6oo; D, X300. 



similar transverse walls are formed before any vertical walls 

 appear, so that the embryo consists of a simple row of cells. 

 As in the Marchantiacese the first wall separates the future 

 capsule from the stalk, and in this respect SpJicEvocarpus 

 approaches the Marchantiaceae rather than the Junger- 

 manniacese. Following the transverse walls there are formed 

 in all the upper cells nearly median vertical ones, which are 

 intersected by similar ones at right angles to. them, so that in 

 most cases (although this is not absolutely constant) the upper 



■* Leitgeb (7), vol. iv. p. 68. 



