GENERA AND SPECIES. 109 
PrATE- XL 
ONOCLEA SENSIBILIS. Linnzus. 
SENSITIVE FERN. 
The Sensitive Fern is the only species of the genus 
found in this country, and though common to the regions 
east of the Mississippi, it has in fact a very limited range. 
Mr. Redfield says, “ Onoclea sensibilis, though absent from 
Europe and most of Asia, appears in Mantchooria and 
Japan. I am not aware that it now occurs in the western 
portion of our own country; but it is a very interesting 
fact that it has been discovered in a fossil state in the 
eocene tertiary of Montana.” * 
It is one of the most common of all our Kentucky ferns, 
and is met with in swamps and marshes, associated with 
the Osmunda regalis and O. cinnamomea. It is sometimes 
called the Oak Fern from the resemblance of its deeply 
cleft leaf to that of the oak. The common name of Sen- 
sitive Fern, derived from its Latin specific name, conveys 
no idea whatever of its peculiar character, as sensibility is 
the very least of its attributes. 
A variety is sometimes found in which some of the pin- 
ne of the sterile frond become contracted and pinnatifid, 
bearing fruit-dots as in the fertile; but I have found, in 
such cases, the sporangia wanting, while next year the 
abnormal frond would resume its original form. It is 
simply a further illustration of the law of morphology, 
which is applicable to every member of the vegetable king- 
dom. It is easily cultivated. The Plate represents a por- 
tion of the sterile frond, with its delicately-reticulated veins. 
* Geograph. Distrib. of Ferns. Bull. Torr. Bot. Club, vol. vi, p. 4. 
