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XXVII. Observations on the Development of the Theca, and on the Sexes of 

 Mosses. By William Valentine, Esq., F.L.S. 



Read May 7th and June 18th, 1833. 



There is, perhaps, no part of the physiology of plants involved in deeper 

 mystery, or about which there is a greater diversity of opinion, than the 

 sexuality of Mosses. Of all the theories which have hitherto been presented 

 to the notice of physiologists, that of the celebrated Hedwig has obtained by 

 far the greater number of followers. He described two kinds of organs con- 

 stituted, in his opinion, for the purpose of reproducing the species, — the male, 

 or spermatocystidium, the female, or pistillum : the former being a peduncu- 

 lated oblong sac, containing a fluid mixed with a granular pulp, which is 

 discharged with some force from the sac on the application of water; the 

 latter, after the admission of the semen mascuUnum by means of the stigma 

 and tubular style, enlarging to form the fruit. All that has been hitherto 

 known about this body is, to use the words of Professor Hooker {3Iuscologia 

 Britann'tca, Introduction, ed. ii. p. 11.), that "the base of one of the pistils 

 gradually swells more and more, and after a certain period the upper part of 

 the style and stigma withers, but still remains. The germen is now seen, 

 covered by a thin membrane, which, as the fructification advances, separates 

 transversely at the bottom, and rising up with the more advanced germen, 

 takes the name of calyptra, or veil. It is carried up by means of a pedicel, or 

 fruitstalk, which now develops itself and reaches to a different height in dif- 

 ferent species, in some being five or six inches in length. When it has 

 attained its utmost development, the mature germen becomes the perfect 

 fruit, and is called the capsule." We find in this passage the opinion that 

 the capsule, or theca as it is now more properly named, is formed in the fii"st 

 instance, and carried upwards by the subsequent development of the fruit- 

 stalk or seta. There are generally several of these pistilla together ; they are 

 vol. XVII. 3 p 



