20 HANDBOOK OF MOSSES. 



membrane of the capsule, and proceed from that to the 

 central body, the columella (fig. 9 c), to which they are 

 attached in every direction, their function being that of 

 holding this in position until the delicate band of cells 

 clothing its outer side are properly developed. The alga- 

 like cells are absorbed before the capsule arrives at maturity. 



Occupying the centre of the capsule, and suspended from 

 the operculum, is a central mass, which consists of two dis- 

 tinct layers of cells; the first and outer layer being that 

 forming the mother cells of the spore band (fig. 9 s\ and the 

 inner mass forming the columella (fig. 9 c). The mother cells 

 of the spores occur as a band or layer of small, opaque cells 

 richly charged with protoplasm, in which is embedded the 

 nucleus. The nucleus, which cannot always be detected 

 without the use of proper re-agents, is attached by proto- 

 plasmic threads to the walls of the containing cell. The 

 band of mother cells of the spores may sometimes be 

 obtained in ribbon-like plates, by pressing the capsule 

 between two glass slips, as in Tortula Iczvipila; but in most 

 instances it breaks up under such treatment. At first each 

 of the mother cells of the spores is filled with protoplasm ; 

 but this granular mass soon becomes divided into four 

 masses, each of which secretes an outer cell wall, and by 

 their growth the original cell wall of the mother cell is 

 absorbed ; they then become free from their attachment to 

 the columella, and float freely in a mucous fluid, which 

 together with them fills the cavity of the capsule. The cells 

 thus formed are the spore mother cells, and these, by a 

 merismatic division of the cell contents, each gives origin 

 to four masses, which in their turn secrete a new cell wall, 

 and by their growth absorb the containing cell wall and 

 become the spores. The mucous fluid is absorbed during 

 growth. In many bryums and orthotrichums the primary 

 cell wall still remains attached until the spores are nearly 

 ripened, holding the spores together, even when fully formed, 

 by these threads of the old cell wall. 



Much interesting information on this head may be gained 

 by examining the inner contents of capsules in the various 

 stages of growth, and this may be most conveniently done 



