GENERAL REMARKS. 



373 



In Gymnostomum, (PI. 112, Fig. II.) there is not even in 

 a very early stage, any inflexion of the inner theca across the 

 stoma to the columella \ but on the contrary, this body totally 

 occupies the whole dimensions of the stoma, the same is the 

 case at the epoch if maturity. 



The inner theca is formed from the columella, in a long 

 section of which a dark line may be visible on either side near 

 the circumference, PI. 1 12 Fig. II., the sporules are not formed 

 at the loss at least of the columella ; for this is larger in the 

 mature fruit than at any other period. The interposition of 

 the sporula causes the inner theca to become gradually ap- 

 proximated to the outer, with which however it does not con- 

 tract any firm adhesion. The columella is originally continu- 

 ous with the outer theca and becomes separated by dislocation 

 of tissufe. This alludes to the period before which the inner 

 theca has become separated. A considerable quantity of aeri- 

 form fluid is contained in the cells forming the irregular 

 inner surface of the outer theca. 



At a very early period there is no trace of the separation of 

 the operculum, but it is completely continuous with what 

 subsequently becomes the apiculus of the columella. 



At a still earlier stage, PI. 1 12. Fig. II., the body of the 

 young theca presents a nearly uniform pulpy green mass, the 

 part corresponding to the operculum and apiculus being 

 white, and more conspicuously cellular. Traces of the separa- 

 tion of the inner columella are yet visible. 



After dehiscence, the columella becomes exceedingly small, 

 will be found, the fundus of the theca. 



My Hymenostylum is a Gymnostomum differing in no im- 

 portant particular, because is some genuine Gymnostoma thp 

 inner membrane at the state of maturity forms an annulus 

 within the external os thecse. 



The margin of this is entire, or nearly so, on the contrary, my 

 Leptostoma, if they have as one would appear to have, decidu- 

 ous membranous epistomata, they will be found different from 

 Gymnostomum, with which Sir W. Hooker has joined them. 



