KNOWLTON: THE STUDY OF FOSSIL FERNS 107 
may supply for the use of the geologist. Right here is a 
point likely to be overlooked by the botanist. Unless 
a fossil fern can be placed with reasonable biological 
accuracy, the botanist is rather prone to look upon its 
study as useless, or at least as not worth the time ex- 
pended in naming, describing, and figuring it. But paleo- 
botany has two distinct phases or fields of study, the 
biological and the geological, depending upon the promin- 
ence to be given to the one or the other of these subjects. _ 
The paleobotanist does the very best he can in correctly 
placing a fossil fern in its relation to the living fm: 
though not infrequently he niay make mistakes, glaring = 
i mistakes; but whether he does oF not. is not of theslight- 
est it to the strat ; geologist so long as_— 
the fossil i is s from a known horizon and is clearly defined 
and capable of being recognized under any and all con- 
ditions. That is to say, if an important coal bed or other : 
geological horizon has associated with it always aper 
ticular and readily recognized | fern, or group of ferns, = __ 
it makes not the slightest difference to the geologist 3 
whether they are correctly or incorrectly named, and 
they might even be referred to by number. — As Prof. 
J. W. Judd once said: “We still si caaie fossils pines he 
* bate 
