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XV. On the existence o/Stomata in Mosses. In a Letter to Richard Horsman 

 Solly, Esq., F.R.S. 8^ L.S. By William Valentine, Esq., F.L.S. 



Read April 3rd, 1838. 



My dear Sir, 



1 CANNOT discover any notice of Stomata having been observed on Mosses 

 in any author within my reach* ; and Professor Lindley states in his Introduc- 

 tion to Botany, and in his Ladies' Botany, that they are not to be found in this 

 order ; and certainly the opinion of their absence is not much to be wondered 

 at, for in by far the greater number of species it is difficult to detect them. 

 Their situation is very remarkable, being confined, with one exception, to the 

 theca. I first detected them whilst examining a section of the theca of Bryum 

 crudum with a triplet. It struck me, from the arrangement of the subcuta- 

 neous tissue of the apophysis in one spot, that a stoma was above it, and upon 

 scraping off the subcutaneous tissue of a portion of the theca, I discovered 

 the stomata in great numbers on the apophysis. I then examined other spe- 

 cies, and found that wherever there was an apophysis they existed, and as in 

 Bryum crudum, only on the apophysis. There appeared to be a very good 

 reason why they should not be found on any other spot, for the apophysis 

 appeared to be the only part having sufficient thickness of tissue to allow of 

 the proper arrangement of the subcutaneous cells ; and this appeared still 

 more striking after examining the apophyses of several species of Splachnum, 

 where they exist in considerable abundance, with one curious exception, 

 S. ampuUaceum, on whose apophysis they are confined to the upper part, 

 which is the only spot where the subcutaneous tissue has not separated from 

 the cuticle. A more extended examination of species seemed to confirm this 

 opinion, but at length the discovery of their occurrence over the whole of the 



* The first discovery of stomata in Mosses is due to Treviranus, who observed them several years ago 

 on the apophyses of Splachnum spharicum, mnioides, ampuUaceum, and in several species of Bryum. Unger 

 {Exanth. der Pflanz. 1833.) has since noticed them in Bryum turbinatum and Bartramia fontana. 



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