INTRODUCTION TO CRYPTOGAMIC BOTANY. 465 



parts of the sporangium folio-wed out from the beginning, shows 

 that the view cannot be correct ; and even supposing the 

 peduncle might produce a leafy shoot instead of a sporangium, 

 a matter very easy to conceive, the external leaves would bear 

 no relation to the internal teeth.* 



512. The spores are not attached, and are without elaters. 

 The mother -cells usually divide into four; but in Eucampto- 

 don perichcetialis (Fig. 99, e) the division goes still further, 

 and the spores appear not to separate when mature. The 

 spores are in general confined to the space between the mem- 

 branous wall of the spore-sac and the columella ; but occasionally 

 some of the cells of the inside of the columella itself are con- 

 verted into spores, as in Syntrichia suhulata.-^ In some Poly- 

 tricha the columella is attached by threads to a waved mem- 

 brane, in the central layer of which the spores are generated. 

 The inner membrane of the spore-sac in other cases does not, 

 therefore, properly belong to the columella. The top of the colu- 

 mella, which is a prolongation of the axis, and which dries up 

 after it has performed its function of nourishing the seed, 

 sometimes forms a sort of membrane, which closes the mouth 

 of the sporangium, as in Polytrichum, and sometimes, as in 

 Dawsonia, is resolved into threads, while in Tetrapliis it splits 

 conformably with the pseudo-peristome. 



513. The genera depend mostly on the nature of the peri- 

 stome, and other details of the fruit. If the plant is annual 

 or biennial, it dies after bearing fruit ; but if perennial, two or 

 more successive crops of archegonia appear. The mode of 

 fructification, therefore, resembles that of Phasnogams with this 

 great difference, that impregnation in the latter produces a 

 young plant from each embryonic cell, while in mosses the 

 impregnation of one embryonic cell produces a sporangium 

 containing a multitude of reproductive bodies, which have no 

 trace of cotyledons or axis. The elaters in Heimticce arose 

 from the development of cells mixed with the mother-cells of 



* See, however, the contrary opinion ingeniously maintained in 

 Lindley's Vegetable Kingdom, p. 65. 



t Lantzius-Beninga, 1. c, tab. 58, fig. 9*. 

 30 



