I50 



SECOND GROUP.— MUSCINEAE. 



into an upper and a lower cell, the latter of the two becoming the stalk, the former 

 the archegonium itself. The mother-cell of the archegonium then first divides by 

 three longitudinal walls into three outer cells, and one central cell which overtops 

 them ; the three outer next form five or six envelope-cells by radial longitudinal walls, 

 while the central cell divides by a transverse wall into an upper cell, the lid-cell, and 



an inner (lower) cell. When the 

 whole structure has grown somewhat 

 longer, it is divided into two stories, 

 the six envelope-cells and the inner- 

 most cell each dividing transversely. 

 The lower story becomes the vefiter, 

 the upper the neck of the archego- 

 nium. The inner cell of the venter, 

 the central cell, increases consider- 

 ably in size, and a transverse wall 

 divides it into a lower and larger cell, 

 the oosphere, and an upper and smaller 

 cell, the ventral canal-cell. Mean- 

 while the upper story, the neck of 

 the archegonium, elongates, and the 

 middle cell divides at the same time 

 into four, eight, or sixteen long nar- 

 row cells, the neck canal-cells. The 

 wall of the venter, which is of one 

 or two layers of cells, is completed 

 by further longitudinal and transverse 

 divisions in its outer cells, while the 

 wall of the neck, consisting ultimately 

 of five to six longitudinal rows of 

 cells, is developed by transverse di- 

 visions of the outer cells of the neck, 

 and the lid-cell divides into five or six 

 cells forming the lid (stigma of au- 

 thors) of the neck. INIeanwhile the 

 original stalk-cell of the archegonium 

 divides by longitudinal walls which 

 cross one another and by transverse 

 walls. During the rejuvenescence 

 and rounding off of the oosphere in 

 the central cell, the longitudinal walls 

 of the neck canal-cells and the trans- 

 verse wall beneath the ventral canal-cell swell up into mucilage, which forces out the 

 protoplasm of all the canal-cells through the opened lid at the apex of the neck 

 (Fig. I go). 



The second generation {sporophore, sporophyte), the sporogonium or sporo- 

 carp, is formed and reaches its full development inside the venter of the arche- 



FlG. loo. Later stages in the development of the archegonia and 

 formation of the sporogonium of Marchantia polymoipha, I—l'IIl 

 magn. 300 times, IX about 30 times. / and // young archegonia. ///, 

 /K after the dissolution of the axile row of neck-cells. K just ready for 

 fertilisation. VII, VI [I the cells of the orifice of the neck x shrivelled after 

 fertilisation, the embryo / showing the first divisions. In these figs, si 

 is the lowest cell of the axile row and the last to dissolve into mucilage, 

 the ventral canal-cell; e in I— IV is the central cell, em I' the oosphere 

 before fertilisation, pp in V, VII, and VIII the developing perig>'nium. 

 I A' is the unripe sporogonium in the venter of the archegonium which has 

 developed into the calyptra ; a the neck of thearchegonium.ywall of the 

 capsule, St its stalk ; inside the capsule are the young elaters like long 

 threads arranged radially, with the spores between them. 



