92 Lnucomplete Adaptation as wlustrated [February, 
gams, was required to be begun anew on the higher Phzenogamic 
plane of development. 
From this point, however, the history of this process is of the 
highest interest. In the Cycadaceze complete dicecism was 
reached before any of the few now existing forms were de- 
veloped, and all present living species are male and female. In 
the Coniferz, different families have attained to different degrees 
of diclinism. The Taxinez, which many facts show to have been 
among the earliest forms developed, are dicecious, while the great 
pine and fir tribes, as well as most cedars, are still monoecious. 
Both these great orders have come down to us from the Carbo- 
niferous epoch, and indicate, along with the remnant which we 
possess of the then luxuriant cryptogamic flora, the kind of vege- 
tation which prevailed in those remote ages. The flowers even 
of the highest forms were uniformly inconspicuous and odorless. 
The only possible substitute for sexual separation was the distri- 
bution of pollen by the winds. Forms so high in development, it 
would seem, could not continue to exist through self-fertilization 
alone, and hence, under the operation of natural selection, more 
or less complete sexual separation early took place. 
The transition from the Gymnos perm to the Angiosperm is 
veiled in great obscurity. Certain considerations point to the 
gradual transformation of the Cycadacez into the Monocotyle 
through: the Palmacez or some allied family, on the one hand, 
and to that of the Coniferae into the Dicotyle through the Gne- 
tacee and Casuarinee, on the other. However this may be, the 
earliest known fossil species of Angiosperms, dating back to the 
early Trias, consist of poplars, beech, oak, chestnut, sycamore, and 
other unisexual and dicecious trees, all of which want the showy 
flowers characteristic of the present flora of the globe. 
In view of the fact that this early flora was to so great an ex- 
tent diclinous, it becomes an important question why so large a 
proportion of the present flora is hermaphrodite. We find that 
many of the plants of the most recent geological development 
possess the means of self-fertilization within the same flower and 
no obvious means of crossing individuals. Upon closer observa- 
tion, however, we perceive that many of these apparently perfect 
flowers possess arrangements of a more or less anomalous kind, 
which, inexplicable on any other theory, are all explainable as 
contrivances for the prevention of self-fertilization. The com- 
