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Darwin Correspondence Project

From J. T. Moggridge   22 August 1873

2 Montague Villas | Richmond | (Surrey)

22 Aug. 1873

My dear Sir

Though I am still some way from the conclusion of my experiments, & from the desired result of rendering the seeds dormant as the ants do, I venture to think that you may like to hear what progress I have made—1

I have devoted most time to the formic acid seed experiments, but I have also tried Carbolic acid,2 the vapour of which I find even more potent in preventing germination than that of formic acid, & oxalic acid,3 which (as far as two experiments go, one with 5 the other with 10 min. of the pure saturated solution) has little or no effect.—

A few experiments with dough (flour & water unboiled, made stiff) go to shew that when the vapour of minute quantities of formic or carbolic acid is present a small gallipot full of dough will remain sweet & free from mildew, when another similar gallipot-full, without the protecting acid vapour, becomes sour & covered with mildew.—

Some curious facts may probably be connected with this, & I hope to make several more observations during the coming winter. When much acid is used the protected dough takes on a salmon tint after a few hours, while the unprotected dough appears unchanged; but in no case have I been able to detect organic life in the protected dough.

I have now two gallipots, one covered with mildew & horribly sour; the other, where 2 min. formic acid in 5 min. distilled water, renewed daily, were placed in a doll’s tea cup supported on a tripod of sticks over the gallipot of dough, quite sweet, though of a faint salmon tint. This experiment was commenced four days ago.

The carefully tabulated results of twenty experiments which I have just completed with formic acid shew conclusively the great influence exercised by the vapour of this acid in either paralysing or killing the seeds, & that the effect produced is proportioned to the amount or strength of acid employed.—

In 16 of these experiments I have made use of Garden Peas, Millet, beet, brocoli & cress; & in the 4 others red clover, marigold, borage, Roman nettle (Urtica pilulifera) & barley; six of each in either case.

The largest amount of acid used was 10 minims pure, & the smallest 2 min. in 712 min. distilled water. The acid was placed in the tumbler on a little saucer or watch glass & not renewed; it gradually became weaker & weaker & less & less therefore, as the experiments lasted from 7 to 12 days. (This was a fault, & I am hard at work repairing it by a new set of experiments.)—

In ten of the twenty experiments, where the acid varied in strength from 10 min. pure to 5 min. acid in 10 of water, no seeds grew & only three beet seeds shewed signs of germination, each putting out a short radicle which quickly died. These attempts at germination were found in one experiment where 5 min. of pure acid had been used & in two with 5 min. acid in 10 of water.

In three experiments, where 5 min. acid in 15 water were used, three peas germinated after some delay in one glass & one of these peas grew.

In one experiment with 314 min. acid in 212 water there was no germination.

In another with 314 min. acid in 5 min. water two of the beet seeds germinated & grew well, three peas also germinated but only one grew

In two experiments with 212 min. acid in 212 min. water two peas & two beet germinated & grew well in one glass, & five peas one millet & two brocoli made an attempt to germinate but did not grow in the other glass.

In the twentieth experiment, where the smallest proportion of acid was used, viz. 2 min. in 712 min. water, all the cress germinated but only two grew; five brocoli germinated & 4 grew well, 5 peas grew well, & all the six millet grains grew well; thus some of all the seeds grew, a result not found in any of the other experiments.

Mildew appeared eventually in all the glasses, but latest in those where most acid had been used. Thus, where there had been 10 min. pure acid mildew did not appear until after 229 hours had elapsed, while in an experiment with 212 min. acid in 212 water it appeared after 141 hours.

It cannot properly be said however that the seeds which have not germinated in consequence of the presence of the formic acid vapour are always killed by it; for I find that, though in some cases decay has set in, in others many seeds appear on dissection to have the embryos perfectly sound.

My experiments lasted from 7 to 12 days, exclusive of the test sowings, which were made for fourteen of the experiments; & each experimental glass was examined twice a day, & this, as the glass cover was taken off on each occasion, caused an increase in the evaporation of the acid & changed the air.—

It appears that peas & beet, which in the control sowing (that made to test the germinative power of the seeds, & in wh. no acid was used) sprouted rather later & more slowly than the cress, brocoli & millet, were the least affected by the acid vapour— This was probably due to the diminished strength of the acid vapour at the time of their germination as compared with that encountered by the more promptly-germinating cress brocoli & millet.

My experiments with small quantities of formic acid renewed daily, or, in the case of very small amounts twice a day, a corresponding measured quantity being placed on a clean watch glass & the former one removed, are for the most part still in progress—

But one thing is quite clear, & that is that the lowest quantity employed in the former experiments is vastly too strong when daily renewed.

I made two of these experiments with six peas & six beet only in either glass, & 5 min. formic acid in 15 water in the one & 212 min. f. a., in 712 water in the other— These experiments were concluded on the eighth day because of the increase of the mildew; the peas were rotting, but the embryos of the beet (protected by a corky, almost woody coat) appeared sound. There was no germination, & the test sowing is hitherto without result.

Again, in experiments with from 3 min. formic acid in 3 min. water to 1 min. acid in 3 min. water, renewed twice a day, no germination has taken place & the mildew is gaining rapidly.

The presence of this mildew is a puzzle & difficulty to me, for I can prevent its appearance on dough with the same amounts of acid.! It also makes me one point farther off from rivalling the ants, in whose granaries mildew is never present.— I should state that in the two control sowings no mildew appeared, so that its presence appears to be due to the indirect effects of the acid vapour.—

I am now commencing experiments with still smaller amounts of acid (formic), such as 12 min. in 5 min. distilled water!

I hope that you will forgive me for troubling you with so long & so dry a statement of the results of my experiments, but I am anxious that you should know that I am not idle, & also eager to take the first opportunity of inviting your criticisms & suggestions—

I have endeavoured to follow your instructions as closely as possible, & there does not appear to me to be any fault in the method unless it be in attempting to place many different seeds together.

I have lately received a curious account of a reference made in the ancient Jewish law to ant’s granaries!—

I am informed that:—“in the Mishna, which is a codification of the Jewish law, & is of great antiquity, the discoverers of Grain stored by the ants are required to pay tithe of the same, as well as other dues, & the conditions under which such ant-stored grain can be consumed as food are laid down”—4

I am now endeavouring to get hold of the exact reference & of a translation of the passage.

Believe me yrs. most sincerely | J. Traherne Moggridge.



After reading Moggridge’s book Harvesting ants and trap-door spiders (Moggridge 1873), Joseph Dalton Hooker had evidently written to encourage Moggridge to experiment on seeds collected by ants to determine what prevented them from germinating (see letter from J. D. Hooker, 20 February 1873 and n. 3). In a letter of 10 March 1873, CD had written to Moggridge to describe experiments he hoped to make, and in July, wrote to him about the progress of his experiments with formic acid (CD’s letter has not been found, but see the letter from J. T. Moggridge, 22 July 1873). Formic acid, which occurs naturally in ant and bee venom, is the simplest of the carboxylic acids and is now used as a preservative in livestock feed.
Carbolic acid or phenol is the simplest member of a class of substances (phenolics) that occur naturally in many plants. For more on the action of phenolics in inhibiting seed germination, see Muscolo et al. 2001.
Oxalic acid occurs naturally in many plants, notably members of the spinach family. Although it is now known to act as an enzyme inhibitor in several seeds, it is deactivated by water. For more on its inhibitory effect, see Morris et al. 1984.
Mishnah Peah 4: 11 deals with ownership of grain in ant holes.


Moggridge, John Traherne. 1873. Harvesting ants and trap-door spiders: notes and observations on their habits and dwellings. London: L. Reeve & Co.


He has added carbolic acid to the seed germination experiments and sends more results on the effect of formic acid. Formic acid inhibits mildew on dough but not on seeds.

Mildew never grows in ants’ nests.

Sends an account, from the Mishnah, of grain stored by ants.

Letter details

Letter no.
John Traherne Moggridge
Charles Robert Darwin
Sent from
Source of text
DAR 171: 222
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9024,” accessed on 27 May 2020,

Also published in The Correspondence of Charles Darwin, vol. 21