itive to the slightest touch. (705/2. In another
connection the following reference to Dionoea is of some interest: "I am
sure I never heard of Curtis's observations on Dionoea, nor have I met
with anything more than general statements about this plant or about
Nepenthes catching insects." (From a letter to Sir J.D. Hooker, July
12th, 1860.)) In our Drosera the filaments are not sensitive to a slight
touch, but are sensitive to prolonged pressure from the smallest object
of any nature; they are also sensitive to solid or fluid nitrogenous
matter. Now in your Drosera the filaments are not sensitive to a rough
touch or to any pressure from non-nitrogenous matter, but are sensitive
to solid or fluid nitrogenous matter. (705/3. Drosera filiformis: see
"Insectivorous Plants," page 281. The above account does not entirely
agree with Darwin's published statement. The filaments moved when bits
of cork or cinder were placed on them; they did not, however, respond
to repeated touches with a needle, thus behaving differently from D.
rotundifolia. It should be remembered that the last-named species is
somewhat variable in reacting to repeated touches.) Is it not curious
that there should be such diversified sensitiveness in allied plants?

I received a very obliging letter from Mr. Morgan, but did not see him,
as I think he said he was going to start at once for the Continent. I am
sorry to hear rather a poor account of Mrs. Gray, to whom my wife and I
both beg to be very kindly remembered.

LETTER 706. TO C.V. RILEY.

(706/1. In Riley's opinion his most important work was the series
entitled "Annual Report on the Noxious, Beneficial, and other Insects
of the State of Missouri" (Jefferson City), beginning in 1869. These
reports were greatly admired by Mr. Darwin, and his copies of them,
especially of Nos. 3 and 4, show signs of careful reading.)

Down, June 1st [1871].

I received some little time ago your report on noxious insects, and have
now read the whole with the greatest interest. (706/2. "Third Annual
Report on the Noxious, Beneficial, and other Insects of the State of
Missouri" (Jefferson City, Mo.). The mimetic case occurs at page 67; the
1875 pupae of Pterophorus periscelidactylus, the "Grapevine Plume," have
pupae either green or reddish brown, the former variety being found on
the leaves, the latter on the brown stems of the vine.) There are a vast
number of facts and generalisations of value to me, and I am stru