From Francis Darwin   [28 May 1876]1

secreting glands of hanstein.2 there were crusts of secretions on some glands & bright globules in others; i thought it would be interesting to see whether the ammonia would not make the protoplasm active, & make a disturbance among the secretion all of a sudden i saw a little blob sticking out beyond the gland, as in fig. 2.

i thought it was secretion, but i cannot swear that it wasn’t there before. anyhow i soon saw it alter its shape, &underwent regular protoplasmic movement.

i thought it must be some kind of amoeba or plasmodium, sticking onto a gland so i looked at the next gland & there was just the same thing   i saw a great ribbon of protoplasm, & to my delight, ablack granule, fig. 3., which walked down it & disapeared in the main body of the mass.3

i afterwads saw the same thing in 5 or6 other glands, though not in every one which i examined. they were always in the same place, viz in the centre of the gland & this does not look at all like a parasite, i think. if it doesnt all come to nothing, it is grand, because it is like the absorption of fat in the intestines by protoplasmic feelers between the epithelium cells. also, a resinous secretion might become a slimy one, then the plant would catch live insects, & the pepsin secretion might be developed—somehow—in a manner better imagined than described. i shall try feeding the protoplasm with vermillion like one does a colourless blood corpuscle, & then it ought to pass into the gland. on reinke principles ought not marginal tentacles of drosera to be serration-glands?4

hooray for theory. blow facts.

yoors affec | f. d.

TLS(A) incomplete

1
The date is established by the relationship between this letter and the letter from Francis Darwin, [31 May 1876], which suggests that Francis last worked on teasel on Sunday; in 1876, the Sunday before 31 May was 28 May.
2
Johannes von Hanstein had suggested that resinous matter (named ‘metaplasm’ by him) was formed in the cells of glands from disintegrating protoplasm, and that this metaplasm was secreted from the cells by means of blister-like cavities that burst to allow accumulated matter to escape (Hanstein 1868, p. 775).
3
After making his discovery that protoplasmic filaments protruded from the glandular hairs lining the cups of the common or fuller’s teasel (Dipsacus sylvestris, now D. fullonum), Francis argued that the secretion of resinous matter occurred while the resin still possessed some vitality, and not by means of blisters as Hanstein had suggested (see n. 2, above) but through the use of filaments (F. Darwin 1877b, pp. 247, 266–7). He noted that the bright red globules were resinous matter found in the glands of second-year leaves (but usually absent from the leaves of seedlings), and that the crust on the outside of the glands was also resinous (ibid., pp. 246 and 265). An amoeba was considered to be a small mass of undifferentiated protoplasm; a plasmodium consisted of several amoeboid cells fused together. The figures mentioned might refer to pencil sketches on the back of the letter, which were largely lost when the pages were cut down to include only the typed text. These observations were also included in F. Darwin 1877b, plate XIX, in which figure 7 is captioned, ‘Gland from specimen which had been mounted about a quarter of an hour previously, in 14 per cent. carbonate of ammonia. It shows the characteristic rounded masses of delicate transparent protoplasm which exhibit amoeboid movements’, and figure 2, ‘Gland bearing a long and stout filament’.
4
Johannes Reinke had observed that in many plants the tips of the serrations on the leaves bore glands that secreted only at a very early stage in the bud (Reinke 1873, pp. 823–5; see also Cross and self fertilisation, p. 403, n.).

Please cite as “DCP-LETT-10515J,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-10515J