To John Scott 2 July 1
Down Bromley Kent
Many thanks for capsules.—2 I would give table of Auricula, especially owing to enclosed extract which you can quote.3 Your facts about varying fertility of the Primulas will be appreciated by but very few Botanists, but I feel sure that the day will come when they will be valued.—
By no means modify even in slightest degree any result.—4 Accuracy is the soul of Natural History. It is hard to become accurate; he who modifies a hair’s breadth will never be accurate. It is a golden rule, which I try to follow, to put every fact which is opposed to one’s preconceived opinion in the strongest light.— Absolute accuracy is the hardest merit to attain & the highest merit.— Any deviation is ruin—
Sincere thanks for all your laborious trials on Passiflora.5 I am very busy & have got two of my sons ill; I very much fear with scarlet-fever;6 if so, no more work for me for some days or weeks.— I feel greatest interest about your Primula cases. I think it much better to count seed than to weigh; I wish I had never weighed: counting is more accurate, though so troublesome.—
Yours sincerely | C. Darwin
Prof. Treviranus says (Botanische Zeitung 1863 p. 4.) that according to Koch & Tausch all species of Primula, present two forms, except P. longiflora which is always short-styled.8
Prof. T. (idem p. 6.) seems to suspect that the long-styled P. auricula is sterile; for he says he found a plant of this long-styled form growing near a short-styled form, & the numerous flowers had not produced a single seed-capsule.
“Various authors have remarked that the Hottonia palustris presents two forms. Fresh Specimens sent to me from N. Wales were grandly dimorphic.10 In the long-styled form, the pistil is more than twice as long as in the other form, & projects far out of the flower; the stigma is smaller & rougher than that of the short-styled: the anthers lie within the tube of the corolla. In the short-styled form, the anthers project far out of the flower & correspond in height with the projecting stigma of the other form; as does the short pistil with the short stamens of the long-styled form.— But the most remarkable difference is in the size of the pollen-grains: those from the short-styled flowers, when distended with water, are 14/14,000 of an inch in diameter; those from the long-styled (& therefore from the shorter stamens) are 9/14,000 in diameter. Spheres differing in the proportion of 14 to 9 in diameter presented under the microscope a most remarkable contrast. The contents of the larger pollen-grains certainly seemed to be coarser-grained & of a browner colour.11
CD’s great interest in JS’s work on fertility of Primula crosses.
Thanks for Passiflora trials.
"By no means modify even in slightest degree any result."
CD wishes he had counted rather than weighed Primula seeds.
Please cite as
Darwin Correspondence Project, “Letter no. 4229,” accessed on 25 July 2016, http://www.darwinproject.ac.uk/DCP-LETT-4229