286 
geological age based on terrestrial and freshwater faunas and floras only 
are extremely likely to be incorrect. 
Unfortunately for us, the deposits in which we are now especially in- 
terested contain few or no marine organisms, but abundant freshwater 
and terrestrial animals and numerous plants. We must therefore reach 
our conclusions by somewhat indirect methods and must be on our guard 
against errors. Still more unfortunately for us, the paleozoologists and 
the paleobotanists have not attained the same results from their studies. 
5. THE VALUE OF PLANTS AS INDICES OF GEOLOGICAL DATES. 
I trust that the paleobotanists will not charge me with trying to dis- 
parage their science when I proceed to show that, in the present case at 
least, their results are less to be depended on than those obtained by the 
prleozoologists. Without doubt, the plants have as interesting, as trust- 
worthy, and as valuable a story to tell, when rightly deciphered, as do the 
animals. It seems, however, that in some cases, other than the one before 
us, the significance of fossil plants has not been rightly comprehended. In 
Blanford’s address, cited above, he mentions two important cases in which 
the determination of the age of certain formations have contradicted those 
made from the marine animals. One case is found in the Gond yana 
system of India, where, as Blanford says, ‘“‘we have a Rhietic flora over- 
lying a Jurassic flora and a Triassic fauna above both.” Again he states 
that “in Australia we find a Jurassic flora associated with a Carboniferous 
marine fauna and overlain by a Permian freshwater fauna.” 
The following is quoted from Lapparent (Traité, p. 718) : 
A plus d’une reprise, l’étude des flores terrestres a paru donner des 
indications contradictoires avec celles des faunes marines; et en derniére 
analyse la question a toujours été tranchée en faveur de ces derniéres. 
Geikie makes the following observation : 
Certainly a number of instances are known where an older type of 
marine fauna is associated with a younger type of flora. 
One reason why plants, at least those of the northern hemisphere, 
which have existed since the beginning of the Upper Cretaceous, seem to 
be of only secondary value in correlating formations is found in their 
apparently extreme conservatism. While the species have changed, the 
genera have changed little. As an illustration of this, one may take the 
list of plants published by Doctor Knowlton (Wash. Acad. Sci., xi, 1909, 
