RECENT WORK ON MOSSES AND FERNS. 363 



sporogenous into cells with a mere vegetative function. 

 For the outer protective wall the evidence of such origin is 

 not conclusive, but for cells lying internally the chain of 

 facts is striking. From the simple Riccia, where all the 

 internal cells develop as spores, the most gradual steps of 

 advance lead on to those forms which have a sterile foot, 

 and elaters scattered through the mass of spores ; and 

 again, to those in which there is a considerable mass of 

 sterile tissue forming- a body like an incomplete columella 

 [Ane7ira, Metzgeria, Pellia, etc.). The details of these are, 

 however, more completely described by Goebel [Flora, p. 1, 

 etc., 1895), an d it appears from his drawings that the fertile 

 tissue becomes localised in these forms as an irregular 

 sporogenous band, surrounding the central but incomplete 

 columella of sterile tissue ; this is a very material advance 

 in the direction of complexity. 



A special chapter is devoted by Campbell to the Antho- 

 ceroteae, which important order he is disposed to remove 

 farther from the Hepaticae than other writers, and he indi- 

 cates for it a place " intermediate between them and Pterido- 

 phytes ". With a simple type of gametophyte, these plants 

 have a sporogonium which consists largely of sterile tissue ; 

 it is green, contains chlorophyll, has stomata, and appears 

 thus as an efficient assimilating body. We thus see the 

 neutral generation advanced towards a physiological in- 

 dependence, which is combined with a long-continued 

 growth ; for water supply, however, it is still dependent 

 upon the gametophyte, having no root-system of its own. 

 Internally the fertile tissue is more strictly localised than in 

 any other Liverworts ; it is referable to a definite layer 

 surrounding the columella, which Campbell shows to be a 

 constant feature. Two points are to be further noted : (1) 

 the archesporial cells are ultimately referable in origin to 

 superficial cells, this is the case also for all Pteridophyta ; 

 (2) the whole archesporial layer does not form spores, but 

 sterile cells are intermixed with the fertile, so that the latter 

 may appear in partially isolated groups (Nototkylas), while 

 the intervening sterile tissue reminds us of the trabecular of 

 Isoetes. 



