Discussion on “ Alternation of Generations .” 111 
Florideae ; the speaker would like to call attention to the effect of 
germination of spores within the sporangium, as observed by Mr. 
Boodle in Todea. This change of conditions led to a precocious 
formation of reproductive organs, while the rest of the body was 
much reduced; similarly in the spore-bearing generation of Riccici we 
had precocious spore-formation and complete reduction of all vegeta¬ 
tive parts, except the epidermis of the spore-sac. To a certain extent 
the comparison might be extended to the Bryophytes generally, but 
the analogy did not help us much with the Pteridophytes. In 
Gymnosperms the female prothallus was retained in the mother 
plant, while it was free in the heterosporous Pteridophytes, but the 
retention did not seem to have had much effect on the prothallus, 
compared, for instance, with that of such a form as Selaginella. In 
the Angiosperms on the other hand, retention of the megaspore 
appeared to have produced a great effect on the prothallus, but 
entirely in the direction of reduction. It seemed a little doubtful if 
there was anything in the retention of the specific cell to account 
for the enormous elaboration of the sporophyte of the higher plants. 
The new view (like the old antithetic theory) seemed to fit the 
Bryophytes better than the Pteridophytes. He would be inclined 
to think that the ancestors of the Pteridophytes already had both 
generations somewhat highly differentiated, and if so, reduction in 
the gametophyte might have played almost as great a part as 
elaboration of the sporophyte in the differentiation of the two 
generations. There was no direct evidence on this question, the 
fossil record did not go far enough back, but the reduction of the 
gametophyte was clearly coupled with land life, for the generation 
that was bound down to semi-aquatic conditions, would have found 
its development cramped. These considerations were perhaps of 
some little importance in comparing the two generations of the 
same plant, a comparison of which one wondered that more had 
not been made before. He supposed the reason was the independent 
modification of the two generations, which had obscured the original 
common characters, so that great difficulties were placed in the 
way of such comparison. 
One of the most interesting things in Dr. Lang’s paper was the 
comparison of early stages in the development of the prothallus and 
of the sporophyte, especially in the remarkable cases of apogamy 
and apospory. He was not quite clear about one point in the 
comparison, namely as regarded the Equisetaceae. He himself 
used to place the Equisetaceae with the Lycopods as primitively 
microphyllous plants. Now he had come to the conclusion 
9.30 that the former were more probably derived from large-leaved 
forms. Dr. Lang’s illustration of the prothallus, with its 
relatively large lobes, did not seem to favour the view that the 
Equiseta were primitively microphyllous, though he gathered that 
Dr. Lang still placed them with the Lycopods as essentially 
microphyllous forms. 
The main thing, from the speaker’s point of view, was that the 
most serious theoretical difference which had divided Professor 
Bower and his school from some of them, seemed to have now 
practically disappeared. He understood that the doctrine of an 
intercalated generation was no longer applied to the Archegoniate 
plants ; intercalation was relegated to some point in the evolution 
of the Algae, and perhaps not very strongly insisted on even there. 
The speaker was not an algologist, and was well content with the 
