28 4 



BRYOPHYTA 



Another Cleistocarpic type, but again one of doubtful affinity, is 

 Archidium, in which the small sporogonium has been examined develop- 

 mentally by Leitgeb. 1 The first stages agree with those of the Phascaceae ; 

 but the tissue of the endothecium shows no differentiation into archesporium 

 and columella : certain few cells of it, definite neither in number nor in 

 position, become spore-mother-cells, while the sterile cells in which they 

 are embedded are absorbed as the spores become matured. This con- 

 dition in Archidium suggested to Leitgeb a comparison with that in certain 

 Liverworts, for instance, Riella ; but in view of the facts ascertained by 



FIG. 140. 



Nanoinitriiun tenerum. Archegonium after fertilisation' and voung sporogonium at 

 different stages of development, in longitudinal section. In II. the endothecium is 

 shaded. F foot ; S = stalk. IV. Sporogonium showing the sporocytes in greater part 

 separate round the columella. All magnified, I. the most highly. (After Goebel.) 



Lang, the comparison with Notothylas would seem more pertinent. 

 Without suggesting even a remote relationship, these two forms both 

 illustrate how individual cells, distributed without order in an otherwise 

 sterile columella, are partially fertile ; and they suggest that the whole of 

 the columella was originally fertile. Of this in the Liverworts there is 

 substantial comparative evidence, and this adds probability to the similar 

 conclusion for the phylum of the Mosses. 



While it is thus seen that in normal Cleistocarpic forms, which may 

 be held to be either primitive or reduced, internal cells of the endothecium 

 may develop as spore-mother-cells, a similar condition is also seen 

 occasionally in Stegocarpic forms as an abnormality : cases have been 

 described of the appearance of fertile cells among the normally sterile 



^Sitz. Akad. Wiss.> Wien, 1879. 



