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XXXI. Supplementary Observations on the Development of the Theca, and on 
the Sexes of Mosses. In a Letter to R. H. Sour, Esq., F.R.S. & L.S. 
By WILLIAM Vatentine, Esq., F. L. S. 
Read May 7th, 1839. 
1 FIND, upon resuming the examination of Mosses, which I had given up, 
that I have not done Mohl justice in the note attached to my paper “on the 
Development of the Theca and on the Sexes of Mosses," published in the 
preceding volume of the Society's Transactions. In that note I have stated, 
that I thought Mohl was mistaken where he describes the sporules as being 
developed by fours in a mother-cell, believing that he had taken the several 
masses of granular contents, which may be in many instances observed in a 
sporule, as so many distinet sporules. I am now bound to confirm the accu- 
racy of Mohl's observation in this respect; and I beg, through you, to offer to 
the notice of the Society a remarkable instance of the tetrahedral union of the 
sporules as an appendix to my former paper. The subject of the following 
account is CZdipodium Griffithianum, which, from my residence being near 
Snowdon, where it is found plentifully, I was enabled to examine in a recent 
state. 
A transverse section of a very young theca (Tas. XXXV. fig. 9.) shows 
several concentric layers of cells in strict contact with each other. The 
outer layer is slightly tinged with brown, and is the true theca: the two 
next, the outer of which is pellucid, and the inner tinged with green granules, 
constitute the thecal membrane. The succeeding layer of cells also contains 
green granules, and the next is pellucid; these two form the sporular mem- 
brane. Independent of the number and sequence of the layers, by which we 
may decide in this state of the theca which will ultimately form the distinct 
sporular and thecal membranes, the presence of the green granules suffi- 
ciently identifies them; for if we examine a longitudinal section of a ripe 
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