164 KANSAS ACADEMY OF SCIENCE. 
this will eventually be demonstrated. He has constantly kept the matter in 
mind during the last three field seasons; but at the present time is reluctantly 
forced to admit that any evidence of plant development from the lower to the 
higher beds of the Dakota is practically wanting. 
That development is shown throughout the various Cretaceous groups, how- 
ever, may scarcely be doubted. The Cheyenne sandstone, 200 feet below the base 
of the Dakota, contains a flora which, in general appearance, resembles that of 
the Amboy clays, or the Tuscaloosa formation, which represent practically the 
oldest dicotyledonous flora known. The types from these horizons show much 
less of development than those found in the Dakota. The Laramie flora, which 
is obtained from beds some 2500 feet above the Dakota, shows considerable ad- 
vance over the Dakota forms. 
The average life of a tree is measured in hundreds of years; that of a marine 
invertebrate will perhaps not average more than twenty years. As trees are 
longer lived, so their forms change more slowly in response to environment than 
animals. The invertebrate fauna of the Cretaceous changes several times from 
the Cheyenne to the Laramie. A number of forms found in the Champion shell- 
bed, a narrow horizon at the base of the Kiowa, do not appear higher in the 
formation. The fauna of the Mentor beds, at the base of the Dakota, is quite 
different from that of the upper Dakota beds, which resemble the Benton fauna. 
By the time the upper Cretaceous groups are reached the fauna has again 
changed. Certain species of plants, however, persist from the Cheyenne to the 
Dakota, and yet others from the Dakota to the Laramie and even almost to the 
present time. When the flora of the Cheyenne sandstone shall have been 
worked up, it should not be thought surprising if it is found that in that forma- 
tion there are species identical with the Laramie or even later groups. While 
these statements are true, it by no means argues that the flora as a whole, or 
even any considerable part of it, is found in different groups. Only a few species, 
comparatively speaking, persist for any great length of time. Each group is 
represented in a large degree by forms which are characteristic of it, and are 
found nowhere else. That plants are more tenacious of life than animals is 
shown by the fact that there are few genera of fossil plants, even of those as far 
back as the Dakota, which are not represented in recent floras. A few genera, 
however, suchas Protophyllum, Aspidiophyllum, and some others, seem to have 
no affinities among living plants. Either their essential characters have been 
gradually effaced by rapid modifications, and so intimately mixed with others as 
to become unrecognizable, or they have been unable to adapt themselves to 
changed environment and have become extinct. 
It is a lamentable fact that plant paleontology has fallen into ill repute both 
among geologists and botanists. The reasons for this are, perhaps, in many cases 
legitimate. The botanist, particularly, having before him all parts of living 
plants—root, stem, leaf, flower, and fruit—is apt to look askance at the work of 
the paleobotanist, who at best has but one of these organs, and that often in an 
imperfect state of preservation. He argues, and apparently with reason, that 
the inferences drawn from such fragmental data are at best imperfect, and con- 
‘sequently misleading; and for this reason is prone to cast aside the work of the 
paleobotanist as of no permanent value. The botanist is right in considering 
that a single fragment of a leaf in an indifferent state of preservation is scarcely 
‘sufficient data on which to found a new species; nor should he admit that slight 
variations in the form, margin or nervation of leaves constitute.specific differences. 
The paleobotanist, on the other hand, insists that while much of his work is 
of necessity incomplete and must be revised in the light of later discoveries, 
