226 On the Gemmce of Bryum androgynum. 



IV. — Observations on the Gemmce of Bryum androgynum. By 

 George Dickie,, Esq. Surgeon, Aberdeen. Plate VII. 

 Bryum androgynum is of rare occurrence in this neighbourhood. 

 It is found growing in the moist earth which fills the crevices of 

 gneiss rocks, generally along with Bryum caespititium. Sir W. J. 

 Hooker, in the second volume of his British Flora, p. 57, remarks 

 that this species is very rarely found bearing capsules, and I have 

 never found it in this state : the reason of this seems very obscure. 

 The gemmae, however, being very plentiful, are quite sufficient to 

 keep up the existence of the species : they are extremely abundant 

 in the months of February, March, and April. These bodies occur 

 in clusters on the summit of a stem bearing much resemblance to 

 the setae in other mosses ; it is, however, of a looser texture, ex- 

 cepting toward its summit, where it presents a swelling and a 

 denser tissue. The swollen part at the summit is easily separable 

 from the rest of the stem, as is represented in Fig. 1, where a part 

 has been removed, the other half remaining with the cords which 

 arise from it. The cords just mentioned, when viewed under a high 

 magnifier, appear to be transparent tubes composed of a simple 

 membrane ; each cord supporting a gemma. The gemmae at the 

 circumference of the clusters are the first to arrive at maturity, 

 those in the centre are developed last of all ; and on the same head 

 we find them in several different stages of their growth. At first 

 they are simple transparent vesicles (Fig. 2,) of an oval form, and, 

 by a high magnifier, no matter can be detected in their interior. 

 As they advance in growth a small stalk becomes evident (by this 

 they are attached to the cords formerly mentioned,) and a grumous 

 matter is seen within, (Fig. 3.) When fully matured they present 

 the appearance shown in Figs. 4 and 5, and the substance in their 

 interior assumes a granular appearance ; it now resembles the mat- 

 ter called green fecula by some authors. The gemmae drop off as 

 they arrive at maturity, those at the circumference of the head first, 

 and so on toward the centre until at last the cords alone remain. 

 It appeared to me to be an interesting matter to determine the 

 process of germination in the gemmae, but considerable difficulty 

 arising from their very small size, for a single gemma is scarcely if 

 at all visible to the naked eye, (the accompanying figures are con- 

 sequently very highly magnified,) the following method was em- 

 ployed. A watch-glass was placed in a saucer with its concavity 

 downwards; over it a piece of fine gauze was spread, the size of 

 which exceeded that of the glass, consequently its edges were in 



