Mosses to he Found in May. 261 



pollen in flowering plants, are safely lodged in rings of mother 

 cells, till the period when they are ready to take an independent 

 position in the field of nature. The layer of sporules being 

 surrounded by the sporal membrane, which consists also of two 

 rings of cells, the outer one containing green granules, the inner 

 pellucid ; and these are again surrounded by the thecal mem- 

 brane, consisting also of two rings of cells, the inner tinged with 

 green granules, the outer pellucid; the size of the space 

 between these two membranes differing not only in different 

 species of mosses, but also in the same species at different 

 periods of growth, being in contact in some, as in Orthotrichum 

 diaphanum, and in others, ' ' of which F. hygrometrica and Bar- 

 tramia pomiformis are," says Mr. Yalentine, " the most marked 

 examples ; they are widely distant, this distance, however, con- 

 stantly diminishing by the growth of the columella and the 

 gradual development of the sporules ;"* and over all is the theca 

 or outer wall, whose cellules are slightly tinged with brown. 



At this early stage the mouth of the capsule is closed up by 

 the lid or operculum, and an intermediate coloured ring, the 

 annulus, formed of large cellular tissue, which, affected by 

 surrounding moisture, causes the lid to fall off, and disclose the 

 beautiful peristome, whose hygrometric action regulates the 

 escape of the ripened spores. The outer row of teeth in this 

 double peristome is a fringy continuation of the thecal mem- 

 brane ; the inner, a like continuation of the sporal membrane. 



Arrived at this stage of maturity, the short branch which 

 bore the fertile flower has become much elongated, overtopping 

 and concealing the barren flower, which will now appear to be 

 at the base of the stem ; and amid the cells of the theca, to- 

 wards the base of the ripe capsule, may be discovered, by a good 

 glass, those little stomata or pores, considered by Mr. Valentine 

 as the necessary apparatus for the admission of air, in order to 

 give greater firmness to the coats of the spores, and the better 

 prepare them for germination. In the young state these 

 stomatas are very small, and much less numerous than when 

 the theca has arrived at maturity ; and in Funaria hygrometrica 

 we have one of the two exceptions mentioned by Mr. Valentine 

 in the Transactions of the Linnean Society, vol. xviii. page 240, 

 in the form of the stomata of mosses, as observed by him. He 

 says : — " Of 103 British species of mosses which I have examined, 

 78 are furnished with stomata, their usual shape similar to the 

 most common form in phaenogamous plants," to which he adduces 

 only two exceptions, Funaria hygrometrica being one, each of 

 whose stomata consisting of a single cell in the form of a hollow 

 ring, with the sides " so compressed as to convert the aperture 

 into a mere slit." 



* Linnean Trans,, vol. xviii. page 241. 



