ii6 MOSSES AND FERNS chap. 



any of the other Bryophytes, Here, instead of the greater 

 part of the sporogonium being devoted to spore formation, and 

 the sporogonium dying as soon as the spores are scattered, the 

 archesporium, especially in the higher forms, constitutes but a 

 small part of the sporogonium, which develops a highly 

 differentiated system of assimilating tissue, with complete 

 stomata of the same type as those found in vascular plants ; 

 and in addition a central columella is present whose origin and 

 structure point to it as possibly a rudimentary vascular bundle. 

 In all of them this growth of the sporogonium is not concluded 

 with the ripening of the first spores, but for a longer or 

 shorter time it continues to grow and produce new spores. 

 This reaches its maximum in some species of Anthoceros, where 

 the sporogonium may reach a length of several centimetres, 

 and continues to grow as long as the gametophyte remains 

 alive. In these forms the foot is provided with root-like 

 processes, which are closely connected with the cells of the 

 gametophyte, from which nourishment is supplied to the 

 growing sporophyte. 



The archesporium produces spores and elaters, but the 

 latter are not so perfect as in most of the Hepaticae. 

 They often show a definite position with regard to the 

 spore mother cells ; this is especially marked in Notothylas. 

 The archesporium in all forms that have been completely 

 investigated arises secondarily from the outer cells of the 

 capsule. Teitgeb's ^ conjecture that in NototJiylas the whole 

 central part of the capsule is to be looked upon as the 

 archesporium, is not confirmed by my observations on N, 

 valvata {orbicularis), where the formation of a columella and 

 the secondary development of the archesporium are exactly as 

 in AntJiocerosr It is hardly likely that in the other species 

 there should be so essential a difference as would be implied 

 by such an assumption. The development of the spores and 

 their germination show some peculiarities which will be con- 

 sidered when treating of these specially. The sporogonium 

 shows no clear separation into seta and capsule, all except the 

 foot and a very narrow zone above it producing spores. At 

 maturity it opens longitudinally by two equal valves, between 

 which the columella persists. The splitting is gradual and 

 progresses with the ripening of the spores. 



1 Leitgeb (7), vol. v. p. 49. ^ See also Mottier (2). 



