This section is from the book "The Gardener's Monthly And Horticulturist V21", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
In the February number of the Gardener's Monthly I see that Mr. C. W. Seelye and Prof. Beal criticise the result, or rather the statement of the result of Mr. Henderson's experiments on Dionaea muscipula. To my mind these experiments of Mr. Henderson's are not entirely satisfactory, from the fact that he appears to have tried them in one way only: that is by feeding the plants with flies, etc., and comparing them with plants not so fed. Now the Messrs. Darwin tried a vast number of experiments in many different ways; still they relied to a great extent on litmus paper as a positive proof that the food was consumed.
It so happens that we have growing wild in this neighborhood thousands of Drosera rotundi-folia, and I have amused myself in trying a few experiments and closely watching the habits of the animal (as Mr. Darwin almost makes it out to be), in its native home. I first procured a few plants and potted them. After they had become thoroughly established in the pots, I commenced to feed them with insects of different species, large insects dead and smaller ones alive. Insects as large as the common house fly must be killed, as their strength is greater than that of the glandular hairs of the trap, and they would escape; but small insects such as mosquitoes if once in the trap are forced to stay there. Whenever I fed a dead insect to a plant I placed another of the same size and species in some secure and similar situation. By this I found that it took exactly the same time for the atmosphere to consume an insect as it took the Drosera, providing the temperature and moisture were the same. I then tried the same experiment on the wild plants with the same results. I next examined the wild plants and found that about fifteen per cent. contained insects and their remains, about twenty-five per cent. contained extraneous vegetable matter, the remaining sixty per cent. nothing.
I could see no difference in size or luxuriance of growth between those containing insects and those containing vegetable matter; but those containing nothing whatever were generally smaller. This I accounted for by supposing that the latter were younger plants, and had neither the surface exposed to catch nor the strength to hold extrenuous matter that the former had. I have read somewhere that if a piece of wood or other uneatable substance be placed within the opening of the glandular hairs of the Dionaea the hairs would immediately close on the substance, but on this being repeatedly done this closing would cease, the plant having found from experience that hard substances were unpalatable. This I tried with the Drosera rotundifolia, but whether my plants being Canadian were sharper, or that they were not in the habit of doing such outlandish tricks, they could not be fooled in that way, no movement of the hairs being perceptible. A small insect placed within the opening was completely entrapped but I could see no movement of the hairs whatever.
The insect, if alive, would die in from twenty minutes to half an hour: Death appeared to take place by suffocation from the clammy fluid exuding from the glands - similar to what would take place if the insect had been covered with oil or honey.
From this and other simple experiments, and from what I can find to read on the subject, I have come to the following conclusions:
1. That the Messrs. Darwin are correct in saying that the Drosera rotundifolia is carnivorous. 2. That Mr. Henderson is correct in saying that no perceptible difference could be seen in the plants he fed and those not so fed. 3. That Prof. Beal's idea that petunias, myrtinias, etc., are carnivorous is also correct. 4. That all plants are carnivorous.
The theory by which I make everybody right and nobody wrong is this: We know that all plants absorb food in the form of carbonic acid, ammonia, etc, through their leaves. We also know that animal or vegetable matter such as beef tea, dead insects, or decaying leaves if allowed to become putrid, throw off a large amount of ammonia, etc. Now if we place any such putrid substance in sufficient quantity in close proximity to any plant, we know that such plant will be benefitted greatly. I apprehend that if Mr. Henderson fed each of his Dionaea plants nearly every day he must have removed the insects given the day before; consequently it could have given off little if any of its gases. Or perhaps he only examined the plants each day and replaced such insects as had decayed. If such were the case each plant would only have received the full benefit of the gases from probably four or five insects during the three months of trial. In either case the benefit would be imperceptible.
In Mr. Darwin's test by litmus paper it is quite probable that the reception by his Droseras of the gases given off by beef tea, would cause an acid reaction in the leaves of the plants.
If Prof. Beal had made a stand directly under the leaves of his plants, and placed putrid beef tea on that stand, he might have noticed considerable difference in the growth of his plants. The fresh beef tea placed directly on the leaves clogged the pores, hence the damaged appearance.
In conclusion, sir, I am well aware that facts, not theories, are what the Gardener's Monthly requires. Still theories are always the forerunners of facts. I am also aware that my theories or ideas are crude; but if they are wrong some of your able writers will soon dispel my illusions, and I shall be well repaid by the knowledge I gain. On the other hand if any part of them be correct, it may help to arrive at the truth, and at the same time entertain your readers. I am sure I have spent many a pleasant hour in the examination of the Drosera, and any of your readers can do the same, as the plants are quite common and can be had for the cost of collecting. As a means of arriving at the truth I would suggest: 1. That the experimenter disabuse his mind as to the correctness of any theory whatever. 2. That a thorough microscopic examination of the structural peculiarities of the Drosera family be made. 3. That all tests made on the plants with food extend during the entire life of the plant. 4. That the results of different foods be noted; also the chemical composition of these foods. 5. That a chemical examination of the soil in which the plants are grown be made both before planting and afterwards.
[We have thought proper to allow a great deal of latitude to our correspondents, and have let them have their say on this question exactly in their own manner and way, without a suggestion or alteration of our own. We cannot now resist the temptation to say that Mr. Forfar's opinions are precisely ours. Mr. Darwin's views have suffered much from the hands of friends who have dealt in the sensational in science. Every one now knows that leaves absorb carbonic acid, and no gardener who has ever grown plants in the heat from a dung bed, and compared their amazing growth with that of plants grown in other artificial heat but must know that they can and do absorb nitrogenous matter in the same way. To us the chief value - and it was great value - of Mr. Darwin's work was that for the first time we had opened to us a view of the manner in which the work was done, and especially in connection with those plants which had sensitive organs. But we could never see why this power in plants should he styled carnivorous in any special sense, any more than that the grape should be specially carnivorous because, as old garedners tell us, it loves a dead carcass when buried near its roots.
We have little doubt but that if some one would try 200 Dionaeas or Droseras in a dung bed, and 200 in an ordinary greenhouse, supposing the temperature and other conditions to be the same, the former would be found as "carnivorous" as any one could expect. - Ed. G.M].