Geologic Correlation.— Ward. 39 
plants. And geologists are apt to reflect their opinions and to 
join with them in condemning paleobotany. 
There are two answers to all these objections. There is an 
answer to the botanist, and a separate answer to the geologist. 
The answer to the botanist is that, considering the conditions 
under which we find these specimens, there really does exist a 
large amount of information of a somewhat exact and reliable 
kind with regard to the past history of vegetation. Aside from 
the fact that at some points on the earth’s surface fossil floras are 
known to exist which almost equal in number of species the ex- 
isting floras of the same localities, there is the further answer that 
paleobotany teaches us to study more carefully the fragmentary 
remains that we find; it sharpens our powers of observation upon 
the facts which are in our possession and has added not a little to 
our knowledge of botany proper. For example, it is the habit of 
botanists to figure leaves so carelessly that the paleobotanist is un- 
able to tell the genera to which they belong. This is chiefly due 
to the fact that they ignore, as a rule, the exact nervation of 
leaves, and are content to figure them almost from the stand- 
point of the artist, merely for the sake of the effect. Paleobot- 
any has taught the botanists that the nervation of leaves is im- 
portant, and that wherever possible it should be carefully figured. 
We are indebted to fossil plants for the discovery that nervation 
in leaves is of generic rank, whereas form, upon which the bot- 
anist chiefly relies, is usually only of specific rank. Leaves, 
therefore, which show nervation are not useless in determining 
species, but are valuable, and by them alone genera may in many 
cases be made out with certainty. 
Still answering the botanist, it may be further urged with jus- 
tice, that in the case of nearly all problematical forms as ancient 
as the Cretaceous, it must not be supposed that the genera can be 
determined by comparison with genera of living plants. It is to 
be expected that the genera with which we are dealing in these 
ancient strata, are extinct, and all that we are called upon to look 
carefully for is evidence of their being related to or the ancestors 
of our modern plants. 
The answer to the geologist is still more conclusive; in fact he 
has no right to raise any objection whatever, It really makes no 
difference to him whether the form that the paleobotanist has 
named, is correctly named or not; this question is one of purely 
biological importance, it is one of no geological importance. But 
