tlie Development of the Thecu, inu] nti the Sexes of Mosses. 501 



to the mother-cells, except that they are more adherent to each other, it is fair 

 to presume that it is by a secretion of granules in their cavities that the addi- 

 tional sporules are formed. I have not been able to find a theca in an inter- 

 mediate state between the formation of the first layer of sporules and the 

 complete conversion of the yellow tissue into sporules. I am not at all cei- 

 tain by what means the four masses of granules in each mother-cell acquire 

 each a separate envelope. It is certain, however, that they gradually become 

 more and more distinct, and their enveloping membrane becomes more opake 

 by a gradual deposition of a granular matter on its surfoce, wliich at maturity 

 is completely covered. This granular deposit has but a loose connexion with 

 the membrane, and is easily rubbed oft' in little grains, which are of a brownish 

 colour when mature, and arc individually transparent, although when crowded 

 over the surface of the sporule they obscure its contents. The contents of the 

 sporules gradually become less and less granular, the smaller grains being 

 apparently absorbed by the larger one, which at length fills the entire cavity 

 of the sporule*. 



The four sporules in each mother-cell are piled on each other, so as to form 

 a cone with a triangular base (Tab. XXXV. fig. 12.), and they appear to be 

 connected with each other in the young state by a very minute stalk which is 

 situated at the conjunction of three radiating lines (Tab. XXXV. fig. 13, 15 



* I have described the contents of the sporules as they appeared at the time ; it did not occur to 

 me, until I had no longer the power of appl}-ing it to this species, that sulphuric acid might perhaps 

 have some effect on the sporules of Mosses. From its effects on Gymnostomum truncuttdum and several 

 otlier species, I am now certain that these large apparent granules are globules of fluid surrounded 

 by a thicker grumous viscid fluid, or I believe I may say, in other words, that they ai-e particles of 

 that fluid separated from its more solid constituents, which separation takes place gradually ; and the 

 globules thus formed, as they increase in size, combine with each other until there is but one large 

 globule remaining, which occupies the entire cavity of the sporule, and is surrounded by the viscid 

 matter of the fluid, which is consolidated into a most delicate translucent pellicle, that forms an elastic 

 internal lining to the sporule. In the cavity thus formed is finally secreted the slimy granular matter, 

 which in Gymnostomum trimratuhim consists of a few granules only; in Tortula rnralis var. hcvipila, 

 the granules and globules of fluid are in about equal proportion ; in Orthotrichum striatum the granules 

 predominate ; and in Jungermannia complanata I cannot discover any traces of fluid, the cavity being 

 filled with gi-anular matter. This fluid is easily observed on account of its immiscibility with water 

 or sulphuric acid. This account of what I conceive to be the modus operandi is of course quite hypo- 

 thetical. 



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