240 
F. E. Fritsch. 
Wildeman, 1 and T. ellipsicarpa, Schmidle var . africana, Schmidle 2 
(Fig. 1, h). 
We can see in this phenomenon a necessary result of the 
terrestrial habitat. The zoosporangia are detached as a whole, 
dispersed by the wind, and only liberate the contained swarmers 
when they come to lie on some moist substratum. The gametangia, 
on the other hand, liberate their gametes in situ, and thus the most 
favourable position for them will be on the creeping base, in close 
contact with the substratum, where inundation must be a frequent 
phenomenon. 
It should also be noted that zoosporangia and gametangia are 
\n some cases found on distinct, though similar, individuals. 3 There 
are thus all the necessary indications for the gradual differentiation 
of two alternating generations, of which the one bears the asexual 
organs on the upright system, the other bears the sexual organs on 
the creeping base. Disappearance of the base in the former, and 
of the upright system in the latter (both phenomena which are 
known to occur among the Chaetophorales) will give two different 
generations, resembling those of the Archegoniatae in all essential 
respects (cf. also the case of Cutleria discussed on p. 15). 
From such a group as the Chastophorales, then, we could 
suppose two alternating generations like those of the higher plants 
to have arisen. We have to picture an ancestor, with well-developed 
base and upright system, from which the two generations gradually 
diverged in the way just indicated. Such an origin, of course, 
amounts to an homologous one, although presumably of a somewhat 
different kind to that in the minds of the adherents to the homo¬ 
logous theory; and the writer may appear, after taking an impartial 
attitude at the beginning, to be caught in the delinquency of 
favouring this view. It does not seem to him, however, that the 
above mode of origin is applicable to the Bryophyta, with their 
completely dependent sporophyte, without forced assumptions. 
It is propounded for the case of the Pteridophyta, and the writer 
realises that he, as little as anyone else, is able to bridge the gap 
between them and their ancestry. 
There is, however, no necessity to seek a separate algal ances¬ 
try for the Bryophyta, as the group of the Chaetophorales also 
’ Les Algues de la Flore de Buitenzorg, 1900, p. 72. 
2 Schmidle, in Engler’s Bot. Jahrb., XXX., 1902, p. 63, Tab. II., Fig. 8 10. 
3 cf. J. Bonnet, in Progressus Rei Hotanicx, V., 1914, p. 101 ; Oltmanns, 
oc. cit., p. 253. 
