232 



HARDWICKE'S SCIENCE. GOSSIP. 



flabb}', two-lobed organ hangs from the end of the 

 hood, right in front of the entrance, which, as I 

 was informed lately by letter from Professor Asa 

 Gray, is smeared with honey on its inner surface. 

 These pitchers are crammed with large insects, 

 especially moths, which decompose in them, and 

 result in a putrid mass. I have no information of 

 water being found in its pitchers in its native 

 country, but have myself found a slight acid secre- 

 tion in the young states of both forms of pitcher. 

 I cannot dismiss Darliiigtonia witiiout pointing out 

 to you what appears to me a most curious point in 

 its history, which is, that the change from the 

 slender, tubular, open mouths, to the inflated 

 close-mouthed pitchers, is absolutely sudden in the 

 individual plant. I find no pitchers in an inter- 

 mediate stage of development. This, a matter of 

 no little signiGcauce in itself, derives additional 

 interest from the fact that the young pitchers to a 

 certain degree represent those of the Sarraceiiias, 

 with open mouths and erect lids, and the old 

 pitchers those of the Sarracenias with closed 

 mouths and globose lids. The combination of re- 

 presentative characters in an outlying species of a 

 small order, cannot but be regarded as a marvel- 

 lously significant fact in the view of those morpho- 



logists who hold the doctrine of evolution 



In what I have said, I have described the most 

 striking instances of ])lants, which seem to invert 

 the order of Nature, and draw their nutriment — in 

 part at least — from the animal kingdom, which is 

 often held to be the function of the vegetable king- 

 dom to sustain. I might have added some addi- 

 tional cases to those I have dwelt upon. Probably, 

 too, there are others still unknown to science, or 

 whose habits have not yet been delected. But the 

 problem that forces itself upon our attention is, 

 how does it come to pass that these singular aber- 

 rations from the otherwise uniform order of vege- 

 table nutrition, make their appearance in remote 

 parts of the vegetable kingdom :— why are they not 

 more frequent, and how were such extraordinary 

 habits brought about, or contracted ? At first sight 

 the perplexity is not diminished by considering the 

 nature of ordinary vegetable nutrition. The roots 

 take up certain matters from the soil. Nitrogen 

 forms nearly four-fifths of the air we breathe, yet 

 plants can possess themselves of none of it in the 

 free uncombined state. They withdraw, in minute 

 quantities from the ground, nitrates and salts of 

 ammonia, and from these they build up with starch, 

 or some analogous material, albuminoids or protein 

 compounds, necessary for the sustentatiou and 

 growth of protoplasm. At first sight, nothing can 

 be more unlike this than a Dioucea or a jS'epentJies 

 capturing insects, pouring out a digestive fluid 

 upon them, and absorbing the albuminoids of the 

 animal, in a form probably directly capable of appro- 

 priation for their own nutrition. Yet there is some- 



thing not altogether wanting in analogy in the case 

 of the most regularly constituted plants. The seed 

 of the castor-oil plant contains, besides the embryo 

 seedling, a mass of cellular tissue or endosperm 

 filled with highly nutritive substances. The seed- 

 ling lies between masses of these, and is in contact 

 with it — and as the warmth and moisture of ger- 

 mination set up changes which bring about the 

 liquefaction of the contents of the endosperm, and 

 the embryo absorbs them, grows in so .doing, and 

 at last having taken up all it can from the exhausted 

 endosperm, develops chlorophyll in its cotyledons 

 under the influence of light and relies on its own 

 resources. A large number of plants, then in their 

 young condition, borrow their nutritive compounds 

 ready prepared, and this is in effect what carni- 

 vorous plants do later in life. The absolute dif- 

 ference between plants which absorb and nourish 

 themselves by the products of the decomposition 

 of plant structures, and those which make a similar 

 use of animal structures is not very great. "We 

 may imagine that plants accidentally permitted the 

 accumulation of insects in some parts of their 

 structure, and the practice became developed 

 because it was found to be useful. It was long ago 

 suggested that the receptacle formed by the connate 

 leaves of Bipsacus might be an incipient organ of 

 this kind ; and though no insectivorous habit has 

 ever been brought home to that plant, the theory 

 is not improbable. Linnaeus, and more lately 

 BaiUon, have shown how a pitcher of Sarraceiiia 

 may be regarded as a modification of a leaf of the 

 Nyhiphcca type. We may imagine such a leaf first 

 becoming hollow, and allowing debris of different 

 kinds to accumulate ; these would decompose, and 

 a solution would be produced, some of the con- 

 stituents of which would diffuse themselves into 

 the subjacent plant tissues. This is in point of fact 

 absorption, and we may suppose that in the first 

 instance — as perhaps still in Sarraceiiia purpurea — 

 the matter absorbed was merely the saline nutritive 

 products of decomposition, such as ammoniacal 

 salts. The act of digestion — that process by which 

 soluble food is reduced without decomposition to a 

 soluble form fitted for absorption — was doubtless 

 subsequently required. The secretion, however, of 

 fluids by plants, is not an unusual phenomenon. 

 In many Aroids a small gland at the apex of the 

 leaves secretes fluid, often in considerable quantities, 

 and the pitcher of Isepenthes is only a gland of this 

 kind, enormously developed. May not, therefore, 

 the wonderful pitchers and carnivorous habit of 

 Nepenthes have both originated by natural selection 

 out of one such honey-secreting gland as we still 

 find developed near that part of the pitcher which 

 represents the tip of the leaf ? We may suppose 

 insects to have been entangled in tlie viscid secre- 

 tion of such a gland, and to have perished there, 

 being acted upon by those acid secretions that 



