THE SENSITJVE AND OSTRICH FERNS. 255 
is so very fugacious that it is seldom seen by any save the 
inquisitive scientist. It is hood-shaped, somewhat like 
that of Cystopteris, and attached to the frond on the 
inferior side of the “ blackberry-like ” sorus. It can be 
found only in the youngest fronds. Part of a fertile 
frond is shown in the Key. : 
At the approach of cold weather, the sterile fronds 
wither but the fertile remain erect all winter. The latter 
are most noticeable against a background of snow-clad 
earth, but would never be taken fora fern by the ordi- 
nary rambler, The berries remain tightly closed through 
the winter and the sporecases commonly do not release 
their spores until spring. Even then the fronds do not 
fall. It is easy to find plants with fertile fronds of three 
seasons still inplace. The spores promptly germinate in 
spring. 
The origin of the common name is involved in some 
obscurity, and several ingenious theories have been ad- 
vanced toaccount for it. One suggests that it has refer- 
ence to the fact that the frond withers so soon after being 
cut; another that it is because the fronds are sensitive to 
autumn frosts. Eaton says that the young fronds are oc- 
casionally cut down by late spring frosts, but this is not a 
common occurrence. There is still another theory which 
accounts for the name by the assumption that the grow- 
ing fronds wither if touched by the human hand, but 
withstand the touch of other bodies. The German 
botanist, Sprengel, is quoted as having proved this by 
numerous experiments, and in Britten’s “European 
Ferns ’”’ we read that “the barren fronds are so thin and 
delicate in texture that they will wither, even when grow- 
ing, if drawn once or twice through the hand.” Those 
who are acquainted with our plant, will no doubt wonder 
