BOG-MOSSES 139 



branch extensively, and detached shoots become inde- 

 pendent growths. The leaves have no midribs, and 

 there is no trace of conducting tissue (p. 134) in the 

 stems; such is not needed in a Moss that can absorb 

 water through any part of its surface, and which grows 

 in a practically aquatic environment. The Sphagnum 

 spore, in germinating, produces at first a very short fila- 

 ment, the protonema, which quickly becomes a flat 

 thallus very like the prothallus of a Fern, which we shall 

 describe in the next chapter; it is from this flat thallus 

 that young Moss plants develop. The sexual organs 

 may occur both on the same plant, or the sexes are 

 represented on different plants; they are formed on 

 branches much like the sterile ones. The branches 

 bearing antheridia are usually distinguishable by their 

 bright colour; it may be dark green, red, or yellow. The 

 leaves are close-set, and the antheridia occur singly in 

 the axils of the leaves. The male organs liberate two- 

 ciliate spermatozoids. The archegonia are found at the 

 tips of short branches at the apex of the plant. The 

 sporophyte, which arises from the fertilized ovum, has 

 no true seta, yet it appears stalked ; the stalk, however, 

 does not rise from the embryo, but from the prolonga- 

 tion of the axis of the female shoot. The capsule is 

 globular, and sits upon an expanded foot. The calyptra 

 is not borne aloft, as in Funaria, but remains, after 

 being ruptured, at the base of the sporogonium, as in 

 the Liverworts. The capsule has a circular lid, which, 

 when the spores are ripe, drops off in order to allow of 

 their dispersal. The form of the protonema in the 

 Sphagnacese suggests that this group of Mosses has 

 arisen from an Hepatic ancestry. It seems probable 



