242 VEGETABLE ORGANOGRAPHY. 



are curved inwards when they are moist, and outwards 

 when dry ; by means of this motion they raise up the 

 operculum, and facilitate the dispersion of the seeds. 



The centre of the theca is occupied by a vertical axis 

 called the Columella, which proceeds from the base 

 and reaches the top of the operculum, to which probably 

 it bears nourishment ; it is sometimes cylindrical, at 

 other times slightly swollen in the middle ; its apex is 

 obliterated at the fall of the operculum. 



The seeds or spores are very numerous, attached, 

 according to Hedwig, to the walls of the theca and to 

 the columella ; they are very small, reddish or brown at 

 maturity, and of a globular or round form. Hedwig has 

 seen those of several species germinate; from his account, 

 the integument breaks, and the young plant presents at 

 its birth a descending filament, which might be taken 

 for a radicle, and a cylindrical divided body, which ap- 

 pears to be a kind of cotyledon; there are afterwards 

 developed kinds of cylindrical and branching primordial 

 leaves, the number of which is uncertain ; they remain 

 for a long time in certain species, as Phascum Confer- 

 voides. Mr. Drummond, who has observed the germina- 

 tion of Mosses since Hedwig, asserts that these confervoid 

 filaments penetrate the earth and form roots. 



This theory of the reproduction of Mosses, although 

 hitherto universally admitted, has not been free from 

 contradiction : some have begun to deny facts upon 

 which there is at present the most accordance ; others, 

 admitting the structure of the organs, have denied the 

 use assigned to them, more, it appears to me, from 

 general opinions upon the absence of sexes in Crypto- 

 gamse, than from the real examination of facts. The 

 principal positive objection has been, that it is difficult 

 to conceive how the female flower, invested with its 

 calyptra, can be reached by the matter emitted bv the 



