The roots are short. Three plants were dug up in North Wales on June
20, and carefully washed; each bore five or six unbranched roots, the
longest of which was only 1.2 of an inch. Two rather young plants were
examined on September 28; these had a greater number of roots, namely
eight and eighteen, all under 1 inch in length, and very little
branched.
I was led to investigate the habits of this plant by being told by Mr.
W. Marshall that on the mountains of Cumberland many insects adhere to
the leaves.
[A friend sent me on June 23 thirty-nine leaves from North Wales, which
were selected owing to objects of some kind adhering to them. Of these
leaves, thirty-two had caught 142 insects, or on an average 4.4 per
leaf, minute fragments of insects not being included. Besides the
insects, small leaves belonging to four different kinds of plants,
those of Erica tetralix being much the commonest, and three minute
seedling plants, blown by the wind, adhered to nineteen of the leaves.
One had caught as many as ten leaves of the Erica. Seeds or fruits,
commonly of Carex and one of Juncus, besides bits of moss and other
rubbish, likewise adhered to six of the thirty-nine leaves. The same
friend, on June 27, collected nine plants bearing seventy-four leaves,
and all of these, with the exception of three young leaves, had caught
insects; thirty insects were counted on one leaf, eighteen on a second,
and sixteen on a third. Another friend examined on August 22 some
plants in Donegal, Ireland, and found insects on 70 out of 157 leaves;
fifteen of [page 370] these leaves were sent me, each having caught on
an average 2.4 insects. To nine of them, leaves (mostly of Erica
tetralix) adhered; but they had been specially selected on this latter
account. I may add that early in August my son found leaves of this
same Erica and the fruits of a Carex on the leaves of a Pinguicula in
Switzerland, probably Pinguicula alpina; some insects, but no great
number, also adhered to the leaves of this plant, which had much better
developed roots than those of Pinguicula vulgaris. In Cumberland, Mr.
Marshall, on September 3, carefully examined for me ten plants bearing
eighty leaves; and on sixty-three of these (i.e. on 79 per cent.) he
found insects, 143 in number; so that each leaf had on an average 2.27
insects. A few days later he sent me some plants with sixteen seeds or
fruits adhering to fourteen leaves. There was a seed on three leaves on
the same plant. The sixteen seeds belonged to nine different kinds,
317