156 MOSSES AND FERNS chap. 



extremely strange if the other species should differ so radically 

 from this one as would be the case were Leitgeb's surmise 

 correct. 



The wall of the capsule does not develop the assimilative 

 apparatus of the Anthoceros capsule, and stomata are com- 

 pletely absent from the epidermis. The inner layers of cells 

 are more or less completely disorganised, and they probably 

 serve to nourish the growing spores, which here, of course, are 

 correspondingly more numerous than in Anthoceros. As in the 

 latter the sterile cells from a series of irregular chambers in 

 w^hich the spores lie. At maturity these sterile cells separate 

 into irregular groups. Their walls are marked with short 

 curved thickened bands, yellowish in colour like the wall of the 

 ripe spores. At maturity the capsule projects but little beyond 

 its sheath, and opens by two valves. In some species, e. g., N, 

 melanospora, the capsule often opens irregularly. 



The Evolution of the Anthocerotes 



The Anthocerotes form a most interesting series of forms 

 among themselves, but are also of the greatest importance in 

 the study of the origin of the higher plants. Unquestionably 

 Notothylas represents the form which most nearly resembles the 

 other Liverworts, but until the other species are investigated 

 further we shall have to assume that the type of the sporo- 

 gonium is essentially different from that of the lower Hepaticse, 

 and corresponds to that of the other Anthocerotes. The pri- 

 mary formation of the columella and the subsequent differentia- 

 tion of the archesporium occur elsewhere only in the Sphagna- 

 cese. From Notothylas, where the archesporium constitutes 

 the greater part of the older sporogonium, and the columella 

 and wall are relatively small, there is a transition through the 

 forms with a relatively large columella to Dendroceros, where 

 the spore formation is much more subordinated and a massive 

 assimilative tissue developed. In Notothylas the secondary 

 growth of the capsule at the base, while it continues for some 

 time, is checked before the capsule projects much beyond its 

 sheath. In Dendroceros the growth continues much longer, 

 although it does not continue so long as in Anthoceros. The 

 assimilative system of tissue in the latter is finally completed 

 by the development of perfect stomata, and the growth of the 



