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Nephrodium molle (Filices).--A seedling fern of this species came up by
chance in a flowerpot near its parent. The frond, as yet only slightly
lobed, was only .16 of an inch in length and .2 in breadth, and was
supported on a rachis as fine as a hair and .23 of an inch in height. A
very thin glass filament, which projected for a length of .36 of an inch,
was fixed to the end of the frond. The movement was so highly magnified
that the figure (Fig. 53) cannot be fully trusted; but the frond was
constantly moving in a complex manner, and the bead greatly changed its
course eighteen times in the 12 hours of observation. Within half an hour
it often returned in a line almost parallel to its former course. The
greatest amount of movement occurred between 4 and 6 P.M. The
circumnutation of this plant is interesting, because the species in the
genus Lygodium are well known to circumnutate conspicuously and to twine
round any neighbouring object.
Fig. 53. Nephrodium molle: circumnutation of very young frond, traced in
darkness on horizontal glass, from 9 A.


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