274 BRYOPHYTA 
the many-layered capsular wall (Fig. 132 F, G, H). The dome-shaped 
archesporial layer divides later into four layers, and every cell undergoes 
the tetrad-division to form spores. At maturity dehiscence takes place 
by a transverse rupture, setting free a circular operculum. The foot is 
considerably enlarged as an haustorium, which is marked off at maturity 
by the narrow neck of the short seta: and the whole is borne upwards 
on a more or less elongated pseudopodium developed by the parent 
gametophyte (Fig. 132 H). 
In the facts thus briefly sketched there is no obvious evidence of 
sterilisation: it is only, when the peculiarly close analogies with the 
Anthoceroteae are traced that any relation to the theory emerges. The 
points of similarity with the typical Anthocerotales are seen in the form 
of the sporogonium, in its absence of apical growth, and in the manner of 
its primary segmentation: also in the origin of the columella from the 
whole of the central group of cells, and of the completely dome-shaped 
archesporium from the primary capsular wall outside it. It differs, how- 
ever, in the mode of dehiscence, and in the fact that elaters are absent, 
while the columella is not mechanically functional: it serves no purpose 
beyond the nutrition of the considerable mass of spores. But as methods 
of dehiscence, and of distribution of spores not unfrequently vary within 
near circles of affinity, this discrepancy does not seem of prime import- 
ance. Lastly, however, there is, as a point of difference from Aznthoceros, 
the absence of any functional assimilatory system in the sporogonium of 
Sphagnum, though it is so well developed in Anthoceros. But, as Haberlandt 
has shown,! functionless stomata, without pores and without intercellular 
spaces below them, are present in large numbers on the capsules of 
Sphagnum: from this he concludes “that it is certain not only that the 
ancestors of the present Bog-Mosses had normal functional stomata on 
their capsules, but also ¢dhat the capsules of these ancestors possessed a 
relatively well developed assimilatory system as well.” All these con- 
siderations taken together point to a close analogy (if nothing more) 
between the two types. 
On the other hand, Sphagnum has always been ranked as a Moss on 
such grounds as habit, absence of elaters, and structure of the archegonium : 
but it differs from all other Mosses in the transverse segmentation of 
the embryo, and in the absence of an apical cell: also (excepting Andreaea) 
in the complete dome-shape of the archesporium, and in its origin from 
the amphithecium; these all being features of correspondence with 
Anthoceros. Such equivocal comparisons, with Liverworts on the one 
hand, and with Mosses on the other, give Sphagnum itself a special 
interest : at the same time they serve to link together the two large groups 
of Bryophytes, and point to the propriety of regarding their sporogonia 
equally from the point of view of a theory of sterilisation. The columella 
would thus be held in both cases to be a consequence of sterilisation 
1 Pringsh. Jahrb., xvii, p. 474. 
