122 MOSSES AND FERNS chap. 



spore formation, and 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 sporophyte 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 sporogo- 

 nium 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 Hepaticse. They 

 often show a definite position with regard to the spore mother 

 cells; this is especially marked in Notothylas. The arche- 

 sporium in all forms that have been completely investigated 

 arises secondarily from the outer cells of the capsule. Leitgeb's 

 ( (7)' V. p. 49) conjecture that in Notothylas 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 develop- 

 ment of the archesporium are exactly as in Anthoceros} It is 

 hardly likely that in the other species there should be so essen- 

 tial a difference as would be implied by such an assumption. 

 The development of the spores and their germination show 

 some peculiarities which will be considered 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 longi- 

 tudinally by two equal valves, between which the columella 

 persists. The splitting is gradual and progresses with the 

 ripening of the spores. 



The genus Anthoceros includes about twenty species, 

 widely distributed, but most abundant in the warmer parts of 



'See also Mottier (2). 



