i88 
NATURE STUDY. 
Ferns and Fern Allies. VIII. 
BY FREDERICK W. BATCHEEDER. 
As noted in the last article, the genus Onoclea, represent¬ 
ed in our area by the sensitive and ostrich ferns, presents 
the phenomenon of dimorphism in its most striking form. 
The fertile leaves are totally unlike the sterile leaves in 
appearance. They are bipinnate, but the divisions of the 
pinnae (the pinnules) are short and small, and each one 
becomes rolled up into a berry-like body which forms a 
sort of involucre to the sporangia borne on its inferior sur¬ 
face. At maturity the pinnules unroll and the spores are 
thus allowed to escape. 
But it is not the extreme dimorphism alone which indi¬ 
cates that the genus is of more ancient origin than the rest 
of our ferns. The geological record furnishes a very re¬ 
markable corroboration of the inferences drawn from the 
present character of the plants themselves. There are fos¬ 
sil remains of the sensitive fern in very perfect condition, 
and these show that this species has undergone very little 
change since the carboniferous era. In fact, this is the 
only fern which has yet been found in the fossil state in 
almost exactly the same form as that in which it is grow¬ 
ing today. The only difference discernible between the 
present and the fossil forms is that in the latter the texture 
of the leaves is more leathery (coriaceous). 
To undertake a systematic description of all the ferns of 
the great family Polypodiacese would transcend the limits 
of Nature Study. Moreover, it would be unnecessary, 
the various text books supplying all need in that depart¬ 
ment of study. While the arrangement of orders and gen¬ 
era in Gray’s Manual has been superseded by the more 
recent one inaugurated by Engler and Prantl, the descrip¬ 
tions of orders, genera and species are in the main to be 
depended on. The student will do better, however, to be- 
