330 



M us CINE M. 



all distinguished by their theca not opening by an operculum, but allowing the escape 

 of the spores only by its decay. While in the genera Phascum and Ephemerum ^ the 

 internal differentiation of the theca corresponds essentially to that of true Mosses, 

 although more simple, the genus Archidium displays a more considerable deviation, 

 and as an interesting transitional form may be examined a little more closely 2. The 

 very short pedicel of the sporogonium swells, as in Sphagnum and Hepaticae ; the 

 roundish theca ruptures the calyptra laterally, without raising it up as a cap. Archidium 

 agrees with the true Mosses in the formation in the theca of an intercellular space 

 running parallel to its lateral surface, which separates the wall from the inner mass 

 of tissue. The latter appears as a colum.n continuous at the foot and apex with the 

 wall of the theca. But while in the true Mosses a layer of cells parallel to this inter- 

 cellular space produces the spore - mother- cells, it is here only a single cell lying 

 eccentrically in the inner mass of tissue that becomes the primary mother-cell of all 



Fig. ■2\'^.— Archidium phascoides ; A longitudinal section of 

 the young sporogonium, showing the mother-cell m of the 

 spores ; B longitudinal section through the young sporogonium 

 with its calyptra and vaginula, /base of the sporogonium, w wall 

 of tlie theca, i intercellular space, c columella, h hollow out of 

 which the spore-mother-cells have fallen, v vaginula, st stem; 

 b leaves, a neck of the archegonium. After Hofmeister (X200). 



Fig. ■2i,^.\— Archiduim phascoides ; 

 longitudinal section through a nearly 

 ripe sporogonium, iu its wall, sp its 

 spores, V the vaginula, b leaves of the 

 stem. After Hofmeister ( X 100). 



the spores (Fig. 243, A). It swells considerably, and supplants the other cells, until 

 it lies free in the hollow of the theca ; it then divides into four cells, each of which 

 produces four spores. The wall of the primary mother-cell remains entire, while the 

 sixteen spores grow, and fill up the whole of the theca, the inner cell-layer of which 

 is also absorbed (Fig. 244). 



4. In the BryaceaB or True Mosses the sporogonium is always stalked, and the 

 pedicel is usually of considerable length. The pedicel {Seta) is cylindrical, obtusely 

 pointed below, and firmly implanted in the vaginula; the theca always opens by the 

 detachment of its upper part as a lid {Operculum) ; the operculum is either simply and 

 smoothly detached from the lower part of the theca, or a layer of epidermal cells 

 term.ed the Annulus is thrown off in consequence of the sw^elling of their inner walls, 

 and the operculum in this way separated from the theca. Most commonly, after the 

 operculum has fallen off, the margin of the theca appears furnished with appendages 

 of very regular and elegant fonn arranged in one or two row^s; the separate append- 



^ J. Miiller, in Jahrbuch fiir wiss. Bot. 1867, vol. VI. p. 237. 



^ Hofmeister, in Bericht der konigl. Sachsisch. Gesellsch. der Wiss. 1854, April 22, 



