and on the Sexes of Mosses. 473 



the fluid from the solid part ; the separation taking place in numberless 

 points throughout the whole mass of secretion. As the little particles of 

 fluid increase in size, the solid material increases in density, until it has 

 assumed the consistence of membrane, which forms an envelope for every 

 separate particle of fluid. Each of these particles, with its investing mem- 

 brane, then detaches itself from its neighbour and becomes an independent 

 cell or sporule. The following are the facts which have induced me to form 

 this opinion. I find upon puncturing the sporular sac of any Moss in the 

 young state, that a quantity of gummy fluid escapes through the puncture. I 

 find also, that the young sporules always adhere together in masses, if care- 

 fully taken out of their natural situation, apparently from being imbedded in 

 an adhesive fluid. The structure of the sporules themselves favours the 

 opinion. In the young state they are remarkably pellucid, and contain a 

 quantity of particles, either in one mass or arranged in thi-ee or four well- 

 dejined smaller masses. These particles I have observed to move with great 

 rapidity. (The species under examination was Bartramia pomiformis.) The 

 formation of these particles takes place either during the formation of the 

 cell or very soon afterwards. I have seen the cell in many instances de- 

 stitute of particles, when, from its extreme transparency, it required a good 

 lens to detect it. The sporule gradually assumes a dark brown colour, and 

 when matiire, becomes more or less opake. In some instances it becomes 

 reticulated ; in others, granulated on the surface. It is difficult to assign a 

 perfectly satisfactory cause for these appearances. The reticulation, perhaps, 

 depends on the increase in size of the particles within (some of them in 

 the young state being much larger than others) ; whilst the granulated 

 appearance seems to depend on the hardening and contraction of the mem- 

 brane. That the sporules are not formed in the columella is clear, as I have 

 frequently dissected off the columeliar membrane; and after carefully washing 

 away the sporules, could never detect any in the columella. In the genus 

 Polytrichum there is a proof still more satisfactory. The columella, in this 

 genus, has a further separation of its tissue into an axis and a middle mem- 

 brane, between which, in the early state, there is a considerable space, tra- 

 versed by horizontal fibres. The connexion which these fibres form between 

 the divided surfaces is similar to that which has been already described as 



VOL. XVII. 3 Q 



