294 EVOLUTION OF PLANTS 
‘The Angiosperms are preéminently the modern plant 
type. These have largely crowded out the other earlier 
types of vegetation, and at present comprise a large 
majority of existing species. In the earlier geological 
formations, Pteridophytes and Gymnosperms predomi- 
nated; but as the later formations are examined, the 
Angiosperms become more and more important, prob- 
ably first appearing in the Mesozoic age and rapidly 
increasing in number and variety in the more recent 
formations. 
It is among the Angiosperms that the plant body 
reaches its highest expression. In the keen struggle 
for existence among the manifold forms of plants, the 
Angiosperms have shown themselves to be extraordina- 
rily plastic, and have developed every possible device 
to enable them to survive this fierce competition. This 
is especially shown in the extraordinary variety of the 
floral structures to which they have given rise. The 
primitive flowers were doubtless very inconspicuous 
and, as in the case of many existing flowers of similar 
character, were dependent upon the wind or upon cur- 
rents of water for conveying the pollen to the stigma. 
This uncertain mode of pollination involves a great 
waste of pollen, and evidently any device which insures 
a saving of pollen is advantageous. This has been ac- 
complished by the adoption of insect aid in pollination. 
This probably began by the casual visits of insects to 
flowers for their pollen, some of which was transferred 
to the pistil of the next flower visited. Any flower 
which, by reason of its brighter color or stronger odor, 
made itself more noticeable to insects searching for pol- 
len, would naturally stand a better chance of being vis- 
