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1897] PHYLOGENY AND TAXONOMY OF THE ANGIOSPERMS 159 
a cucumber (Cucumis), a sunflower (Helianthus), a water-plan- 
tain (Alisma), an arrow-head (Sagittaria), a lily (Allium), an 
oat (Avena), and a wheat (Triticum), and when the young 
plants first appear they will be recognized merely as five dicoty- 
ledons and five monocotyledons. But a little later the butter- 
cup, Clematis, and potentilla will separate themselves from the 
cucumber and sunflower, the former resembling one another 
very much, and having a common buttercup-like look, while the 
latter resemble one another nearly as much. The families to 
which the seedlings belong will be indicated next, but it will 
take longer to separate the potentilla from the buttercup and 
clematis than the cucumber from the sunflower. The buttercup 
and clematis will be generically indistinguishable much longer, 
and had we planted seeds of different species of one of these it 
would have been still longer before differential characteristics 
would have appeared. So too with the monocotyledons, the 
families can be recognized long before the genera, and the gen- 
era long before the species. 
Now what do these facts indicate? How can we make use 
of them in our present inquiry? Is it not highly probable that 
they indicate how and when the differentiation of species from 
species, of genus from genus, of family from family occurred? 
If we grow two plants side by side and find them to be indis- 
tinguishable until they have formed their fruits, are we not war- 
ranted in regarding the relationship a very close one, and may 
we not safely assume that the separation is a relatively recent 
accomplishment? There can be no valid objection to the rule 
that the greater the number of stages of identical development 
between plants the closer the relationship. This is but another 
way of expressing the common working rule of botanists that 
close relationship is shown by the identical structure of many 
Organs. When we know the life history (ontogeny) of a group 
of plants, and have brought these together so that we shall 
have well wrought out the comparative ontogeny of all the 
Species, we shall be able to indicate with much exactness their 
mutual relationship. And when this is done for all of the 
