2 SPHAGNACE^. 



of the branches usually has in addition an outer series of flask 

 shaped cells, the retort cells, slightly narrowed above into a neck 

 which is frequently more or less recurved from the branch ; thi 

 is markedly the case in S. tenellum. 



The stem leaves are thin and fragile, differing in form ant 

 structure from those of the branches. The branches are ii 

 fascicles of from 3 to 12, generally of two forms, some beinj 

 pendent and more or less appressed to the stem, usually longe 

 and more flagelliform than the others, which are divergent^ mon 

 spreading or even ascending, and for the most part stouter, 

 with shorter and broader leaves. The branches at the apex o 

 the stem are as a rule more densely crowded and shorter, forming 

 a more or less compact head, the capitulum. 



The areolation of the branch leaves is very remarkable. I 

 consists of a single layer of cells of two forms, alternating witl 

 one another ; the true cells being very narrow, more or less 

 chlorophyllose, and almost hidden between the larger ones, the 

 utricles or hyaline cells, which are usually sinuosely elliptical oi 

 rhomboid, and with rare exceptions contain spiral fibres or mon 

 accurately spiral thickenings of the cell walls ; the walls are alsc 

 perforated by rounded pores. The stem leaves differ in theii 

 tissue being entirely composed of hyaline cells, possessing much 

 fewer fibres and pores, which may indeed be altogether absent. 



The antheridia are remarkably like those of the foliose 

 Hepaticae, and are hardly approached in structure among the 

 mosses, except perhaps in Buxbaumia. They are stalked 

 globular, and lie singly in the axils of the bracts, usually at the 

 apex of specialised branches of the capitulum, called amentula 

 The paraphyses are very finely capillary, and are branched. 



The female flower is formed as a bud on the stem in the axi 

 of one of the upper fascicles. After fertilisation the perichaetia 

 bracts elongate so as to give the whole the appearance of a 

 short lateral branch, while the basal part of the sporogonium 

 which may be termed the vaginula, elongates rapidly into 1 

 "pseudopodium" upon which the ripening sporangium is elevatec 

 above the perichaetial bracts. The mature capsule is almosl 

 uniform in all species of Sphagnum, of a chestnut brown, globose 

 or elliptical, with a flatfish or convex lid which separates suddenl} 

 at maturity by contraction of the walls of the capsule. The 

 calyptra is very delicate, and is irregularly torn in separating froir 

 the vaginula by the growth of the sporogonium. The spore: 

 are of two kinds, the one much larger than the other. On germin- 

 ation these — the macrospores at least— give rise to a flat frondose 

 prothallium. 



