On antithetic as distinct from homologous 
Alternation of Generations in Plants. 
BY 
F. O. BOWER, D.Sc., 
Regius Professor of Botany in the University of Glasgow. 
‘HERE are few subjects within the scope of Biology 
JL which have given rise to so much divergence of 
opinion, and at the same time so great obscurity of con- 
ception as that of 1 alternation of generations.’ For more 
than half a century the fact that within the narrow limit of 
the ontogenetic cycle, like does not always directly produce 
like, has been known and discussed, the discussion most 
frequently taking the form of mere comparison of the suc- 
cessive phases of various organisms, with but slight reference, 
if any, to the external circumstances under which the organ- 
isms grow, or to their relationships by descent. At the 
present time, knowing as we do how profoundly the environ- 
ment affects the conformation of the organism, it is imperative 
that in the discussion of the phenomena of alternation such 
considerations should be constantly kept in mind, and especially 
the differences of external conditions of the organisms in which 
alternation is seen. 
Before the days of the theory of evolution, when the idea 
of uniformity of type in organic creation held stronger sway 
over the minds of biologists than now, it was natural that the 
attempt should be made, by coercing facts into correspondence, 
to draw comparisons where they are not warranted : even 
among those who accept evolutionary views, the tendency 
[Annals of Botany, Vol. IV. No. XV, August 1890.] 
