Feb., 1909.] The Classification of Plants, IV. 45 1 



elastically elongating stalk; sporangium without columella, 

 usually with elaters, indehiscent, irregularly dehiscent at the top, 

 or splitting into four valves from the summit, rarely developing 

 an operculum. 



27. Sphagneae. Bog-mosses. 250 species. 



Gametophyte a stem-like, erect, light, gray-green frond with- 

 out a true central strand but with large cortical cells, bearing 

 numerous scales without a costa but with two kinds of cells, 

 narrow ones with chlorophyll and large ones without, but with 

 holes in the walls ; rhizoids septate ; protonema finally thalloid and 

 fiat; fruiting plant developing one or more pseudopodia which 

 support the sporoph3-tes. Sporophyte without a stalk but 

 with an expanded foot ; sporangium with a shallow dome-shaped 

 spore cavity in the upper part and with an operculum but with- 

 out a peristome, elaters, or air cavities. Growing in bogs and 

 wet places. 



28. Andreaeae. Granite-mosses. 105 species. 

 Gametophyte a stem-like, erect frond without a central 



strand, bearing numerous scales without or with a costa; rhi- 

 zoids consisting of cylindrical masses or plates of cells ; protonema 

 more or less thalloid. Sporophyte without a seta but with a foot 

 and finally carried upon a pseudopodium; sporangium without 

 air cavities, splitting into four or more valves which are at first 

 united at the top, spore cavity cylindrical dome-shaped with an 

 upward projecting central columella; elaters none; calyptra pre- 

 sent on the sporophyte. Caespitose plants of a dark brown color 

 growing on rocks. 



29. Musci. Mosses. 12,500 species. 



Gametophyte a stem-like, erector prostrate frond usuallvwith 

 a well-developed central strand and with costate scales ; rhizoids 

 filamentous, septate; protonema usually well-developed and fila- 

 mentous, sometimes persistent; pseudopodium none. Sporo- 

 phyte well-developed with sporangium, foot, and usuallv with 

 a well-developed hypophysis and a seta with a central strand; 

 sporangium usually with an operculum and a central columella 

 extending entirely through the spore cavity, usually with a well- 

 developed peristome and air spaces often communicating on the 

 outside with stomata; venter of the archegonium enlarging and 

 usually ruptured at the base, the upper part being carried on top 

 of the sporangium as the calyptra. 



30. Anthocerotes. Horned Liverworts. 10.3 species. 

 Gametophyte a dorsiventral thalloid frond without scales or 



with imperfectly developed scales but with unicellular rhizoids; 

 sexual organs imbedded in the tissue of the thallus; protonema 

 small and transient. Sporophyte with a slender horn-like or 



