342 PART IV. CLASSIFICATION. 



layer of cells, and has numerous stomata. The capsule opens by the 

 throwing off of the apical portion of the wall as an operculum. There is 

 no peristome. 



When the cal3*ptra is ruptured, it remains as a vaginula round the 

 base of the capsule. No part of it is carried upon the top of the capsule. 



The growth of the archegoniophore is stimulated by fertilisation. It 

 grows (Fig. 206 j?i) out at its apex into a long leafless stalk, the pseudo- 

 podium, expanded at the top into a cushion of cells in which the foot of 

 the sporogonium is embedded ; the perichsetial leaves grow and surround 

 the base of the stalk. 



The order consists of the single genus Sphagnum, of which there are 

 very many species. 



Order II. Bryineae. 



A. The G ^METOPHYTE. The protonema is filamentous, though in some 

 cases (e.y. Tetraplris pellucida) it developes flattened cellular appendages 

 which are assimilatory organs. The subaerial portion of the protonema 

 is generally short lived, though in some cases it persists (e.g. Ephemerum) 

 at least until the sporogonium has been developed and the spores 

 are ripe : the subterranean portion frequently persists from year to year. 

 The subaerial portion gives rise to the gametophores as lateral buds ; in 

 some forms the subterranean portion produces lateral buds in the form of 

 bulbils (p. 332) which, when* they are brought to the surface, give rise to 

 gametophores either directly or indirectly with the intervention of 

 protonema. It is commonly the case that, when protonema is kept dry, 

 some of the cells grow larger and their walls thicker, whilst the other 

 cells perish ; the persistent cells, when moistened, develope into filaments. 



The Adult Shoot does not present, with regard either to its morphologj- 

 or its histology, any especially characteristic features ; it varies in size 

 from a mere bud in such forms as Phascum and Ephemerum, where it is 

 annual, to a shoot several inches long in such forms as Fontinalis and 

 Polytrichum where it is perennial. In the latter case there is general 1}- 

 a central strand, and frequently leaf-traces, in the stem. It may be 

 either acrocarpous or pleurocarpous, a feature which is important in the 

 classification of the group. The leaves have commonly a midrib : the 

 lamina generally consists (e.g.. Funaria, etc.) of a single layer of cells. 

 The leaves of Leucobryum resemble those of Sphagnum in that they 

 consist of two kinds of cells, an internal layer of small living cells with 

 chloroplastids, and external layers of dead cells with perforated walls ; 

 the peculiar structure of the leaves of Polytrichum has been alread}- 

 described (p. 336). 



B. The SPOROPHYTE presents features, both as to its morphology and 

 histology, which are characteristic of the group. It is differentiated into 

 a true hypobasal foot, a seta, and a capsule. The true foot is rudi- 

 mentary. The seta is relatively short in the lower forms; a false 

 (epibasal) foot is frequently developed from the lower portion of the seta. 

 The neck of the capsule has nearly always stomata in its epidermis, 

 and is developed into a distinct apophysis in some forms ( e.g. Splachnum, 

 Polytrichum). Part of the external layer of the endothecium becomes 



