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ON THE DEVELOPMENT OF THE THECA, AND ON THE SEXES 



OF MOSSES. 



Every vegetable anatomist is acquainted, more or less, with the researches of 

 Mr. Valentine, and with the accurate and philosophical conclusions at which he 

 has arrived. It was by his beautiful and perfect preparations of spiral vessels 

 (together with those of Mr. Griffiths), that their actual formation became known ; 

 a subject which, until that period, had been involved in considerable obscurity, and 

 upon which the most distinguished botanists of the age were divided in opinion. 

 Since that time the attention of Mr. Valentine has been directed to the mode in 

 which the theca of mosses is developed, as well as to the peculiar structure of those 

 minute and delicate organs which are destined for the reproduction of the species ; 

 a subject which hitherto had been but very imperfectly understood. The result 

 of his investigations he has given in a paper read before the Linnean Society in 

 1833, and published in the 18th volume of their Transactions* ; from which we 

 shall beg leave to make the following extracts, in order to make our readers 

 acquainted with the discoveries of that most accurate vegetable anatomist in a 

 highly curious and interesting subject. 



Mr. Valentine begins by observing that " 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." He then states that the theory 

 which has obtained by far the greater number of followers is that of the celebrated 

 Hedwig, who described two kinds of organs— the male, or spermatocystidium, and 

 the female, or pistillurn ; the latter of which, becoming enlarged from impregnation 

 by the former, forms the fruit. All that has been hitherto known about this body, 

 continues Mr. Valentine, is, to use the words of Professor Hooker ( Muscologia 

 Britannica, 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 fruit-stalk, which now develops 

 itself, and reaches to a different height in different 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, says Mr. Valentine, 

 in this passage the opinion that the capsule, or theca, as it is now more properly 

 named, is formed in the first instance, and carried upwards by the subsequent 

 development of the fruit-stalk or seta. There are generally several of these pistilla 



* Observations on the Development of the Theca, and on the Sexes of Mosses. By William Valentine, Esc. 

 F.L.S. 



