The Evolution of Plants. 
7 
indifferent success, the same problem that the Proto-archegoniate 
solved satisfactorily. The “ exaggerated ” neck of the archegonium 
the author compares with the pseudostylar micropyle of certain 
Gymnosperms and the stylar tube of Angiosperms. 
Thus the essential features of the archegonium and of the 
antheridium appear an evolution of a multicellular fertile algal 
branchlet (the first beginnings of which appear in Dictyota ), in 
response to the conditions of subaerial life, obtaining incidentally 
the advantages of the oogamy and of fertilisation and development in 
situ , advantages which the Florideae (and Chara) in part have 
obtained in other ways. 
The archegonium is polyphyletic in origin, and never existed 
in a condition of completely submerged algal benthon. Not only 
the Bryophytes but also different phyla of Pteridophytes are to be 
traced back to distinct origins, not only among marine benthon, 
but to distinct flagellate plankton ancestors. This conclusion was 
already suggested by the work of Bohlin and Luther (1897-1901) 
on the zoospores of algae, though few students of the Archegoniatas 
have been bold enough to follow out its full consequences, which 
involve the derivation from distinct flagellate types, not only of 
Perns and Lycopods but also of Equisetales, and perhaps of Isoetes, 
though the octokont zoid of this genus may be derived from the 
isokont type. The whole trend of modern morphological investi¬ 
gation, indeed, encourages us not to be afraid of postulating far- 
reaching extension of independence of origin with convergence and 
homoplasy; and such postulates may justifiably be carried to a 
point which would have scandalised the older morphologists. 
The origin of the archegonium and antheridium is only one 
problem raised by a consideration of the evolution of the 
reproductive mechanism of the green land plants. The 
sporogonium of the Bryophyte Mr. Church regards as the reduced 
form of a benthic radially organised shoot, from which, he thinks, 
the leaves have disappeared, leaving the photosynthetic mechanism 
on the axis. He strongly upholds Bower’s contention that radial 
organisation is primitive, and insists that it originated as a response 
to the benthic conditions of life, since it is the common type among 
seaweeds. Dorsiventrality in land plants, for instance in the 
dichotomous dorsiventral liverworts, he regards as an evidence of 
degeneration or perhaps of derivation from degenerate dorsiventral 
seaweeds. The photosynthetic and transpiratory structures of 
sporogonia must either have been evolved independently of the corre« 
