230 BOTANICAL GAZETTE [SEPTEMBER 
which represent the primitive types, and that it is less marked 
between the higher members of the groups. In other words, we 
recognize the fact that groups diverge as they are evolved. If 
we represent the phylogenesis of plants by lines, we are com- 
pelled to arrange these lines so that they show repeated series 
of divergencies. 
Another law which must be kept in mind, also, is that evolu- 
tion for the most part has proceeded from the simple to the 
complex. The simpler plants of today represent to a large 
extent the types of the primitive plants of former periods, from 
which the complex plants of today were derived. In this con- 
nection, however, we must not overlook the fact, as pointed out 
elsewhere,’ that in the evolution of the successive members of 
groups of plants there has often been a simplification of structure. 
Thus we often find apetalous derivatives from polypetalous types; 
bicarpellary ovaries from polycarpellary types ; one-celled, one- 
seeded compound ovaries from several-celled, many-seeded 
ovaries. But there is a great difference between these simplified 
structures which have been derived from more complex struc: 
tures, and those which are primitively simple. The former are 
nearer the end of a lengthened genetic line, the latter are nearet 
its beginning. 
When we apply these principles to the system of Bentham 
and Hooker we find no contact points whatever between mon 
ocotyledons and dicotyledons. The lower monocotyledons are 
very unlike any of the Apetale. What similarity, for example 
is there between the grasses and sedges, on the one hand, an 
the oaks, walnuts, and plane trees, on the other. It is only whee 
aa pass up to the Apocarpe in the monocotyledons and to the 
Micrembrye, and possibly Piperaceee of the latter, that there 
are many similarities of structure. To this I must refer later 
and need only Say here that evidently the authors made n° 
attempt to indicate by their arrangement of families any contact 
point between the monocotyledons and dicotyledons. 
* Evolution and Classification. Proc. A. A. A. S. 42:237. 1894, and The signif- 
cance of the compound Ovary, presented at this meeting. 
