F. E. Fritsch. 
THE ALGAL ANCESTRY OF THE HIGHER PLANTS. 1 * 
By F. E. Fritsch, D.Sc. 
[With Two Figures in the Text]. 
I N all of the groups, above the level of the Thallophyta, the life- 
cycle is characterised by the succession of two individuals— 
the one sexual, the other asexual—in regular alternation, and the 
origin of these two alternating generations has long been the sub¬ 
ject of discussion. One group of Botanists, with whom we may 
couple the names of Pringsheim and Scott, 3 have held that the two 
generations are homologous, having arisen by gradual differentia¬ 
tion from an indifferent .generation bearing both asexual and sexual 
organs, such as is commonly found in the Algae at the present 
day. 
Other authorities, especially Celakovsky and Bower, 3 hold that 
the sporophyte is a new intercalation in the life-history, originating 
by a gradual elaboration of the zygote, i.e., it is antithetic to the 
gametophyte. 
Such evidence as has been adduced speaks neither for the one 
nor for the other view; in the case of the Pteridophyta the balance 
is, perhaps, in favour of the homologous theory, in the case of the 
Bryophyta more in favour of the antithetic. Nor does it seem 
necessary to postulate the same mode of origin for the two groups, 
a point of view that has not, perhaps, received sufficient considera¬ 
tion. 4 * The differences between the sporophyte in Bryophyta and 
Pteridophyta are very marked ; in fact, the only important resem¬ 
blance is the differentiation of stomata of a similar type.* 
In 1909, Lang 6 put forward a theory of alternation, the essence 
of which is to explain the differences between the two generations 
as being due to the retention of the spore (whether asexually or 
sexually produced) within tiie body of the parent-organism for a 
longer or shorter space of time. Lang’s theory would appear to 
1 Presidential Address to the Intercollegiate Botanical Society, University 
of London. 
1 cf. Presid. Address, Bot. Sect., Brit. Assoc., Liverpool, 1896. 
3 Annals of Botany, IV., 1890, p. 347. 
4 cf. however Tansley, in New Phytologist, XI., 1912, p. 216. 
6 Recalling the development of structures closely resembling the sieve- 
tubes of the Angiosperms in such' Laminariaceas as Macrocystis, it is evident 
that like demands may lead to the differentiation of similar structures, with¬ 
out implying any close relationship. 
6 W. H. Lang. A theory of alternation of generations in Archegoniate 
plants based upon the ontogeny. New Phytologist, VIII., 1909, p. 1. 
