MOSSES. 



329 



Mosses ; several of them are usually fertilised in one perichuetium, but only one 

 perfects its sporogonium. This development occurs within the perichsetium ; the 

 summit of the branch then begins to rise, grows out into a long naked receptacle, 

 and elevates the sporogonium contained in its calyptra high above the perichcetium. 

 This so-called Pseudopodium must not, however, be confounded with the seta of 

 other jMosses. At Fig. 242, 5, is shown in longitudinal section the nearly ripe sporo- 

 gonium developed within the calyptra. Its lower part forms a thick base imbedded 

 in the end of the pseudopodium wTiich is transformed into the vaginula. The origin 

 of the spore-mother-cells is a cap-shaped layer of spherical cells beneath the apex of 

 the spherical theca ; the part of the inner tissue which is found beneath it forms a 

 low nearly hemispherical column, which 

 is in this case also termed the Columella, 

 although it is distinguished from the colu- 

 mella of true Mosses by not reaching to 

 the apex of the theca. The mode of the 

 formation of the spores from the mother- 

 cells resembles that of true Mosses ; but 

 there occur, besides the ordinary (large) 

 spores, also smaller spores in special smaller 

 sporogonia, which owe their origin to a 

 further division of the mother-cells (r/". 

 Fig. 237, E). The theca opens by the 

 detachment as a lid of the upper segment 

 of the ball, which is sometimes more 

 strongly convex. The calyptra, which 

 closely surrounds the growing sporogo- 

 nium as a fine envelope, is ruptured irre- 

 gularly. 



2. The Andreaeaceae * are small ccspi- 

 tose Mosses which are very leafy and 

 much branched ; their very shortly stalked 

 theca is elevated, as in Sphagnum, above 

 the perichffitium on a leafless pseudo- 

 podium. The long apiculate theca raises 

 up the calyptra in the form of a pointed 

 cap, as in the true Mosses, while the short 

 seta remains buried in the vaginula. The 

 body of the young sporogonium becomes 

 differentiated into a parietal tissue con- 

 sisting of several layers which surrounds 

 the simple layer of the spore-mother- 

 cells without any intermediate cavity, 

 and a central mass of tissue, the colu- 

 mella ; in the same manner as in the 



Sphagnaceae the layer of cells which produces the spores is bell-shaped and closed 

 above, the columella terminating beneath it. The ripe theca does not open by an 

 operculum, but by four longitudinal slits at the sides ; four valves are thus formed 

 united at the apex and at the base, which are closed in damp, but open in dry 

 weather. 



3. The Phascaeeae are small Mosses, the short stems remaining attached to the 

 protonema until the spores are ripe ; they may be considered as the lowest form of the 

 following group, to which the genus Phascum forms the transition. They are, however. 



Fig. 242. — A, P, SphagJiiim acidifoliitfn ; A longitudinal 

 section of the female flower, ar archegonia, ch perichsetial 

 leaves still young, jv the last perichretial leaves or perigynium ; 

 B longitudinal section of the sporogonium sg, the broad base of 

 which sg' remains in the vaginula v, while the capsule is sur- 

 rounded by the calyptra c, upon this is the neck of the arche- 

 gonium ar, ps the pseudopodium ; C Sphag7uim sqiiarrosmn, 

 ripe sporogonium sg with its lid d and ruptured calyptra c, qs 

 the elongated pseudopodium growing from the perichsetium ch 

 (after Schimper). 



J. Kuhn, Zur Entwickelungsgeschichte der Andreaeceen, Leipzig 1870. 



