Sept. 3, 1874] 



NATURE 



371 



fully formed pitcher that has not received animal matter, it forms 

 again, but in comparatively very small quantities ; and the for- 

 mation goes on for many days, and to some extent even after the 

 pitcher has been removed from the plant. I do not find that 

 placing inorganic substances in the fluid causes an increased 

 secretion, but I have twice observed a considerable increase of 

 fluid in pitchers after putting animal matter in the fluid. 



To test the digestive powers of Nepenthes I have closely fol- 

 lowed Mr. Darwin's treatment of Dionixa and Drosera, employing 

 white of egg, raw meat, fibrine, and cartilage. In all cases the 

 action is most evident, in some surprising. After twenty-four 

 hours' immersion the edges of tlie cubes of white of egg are eaten 

 away and the surfaces gelatinised. Fragments of meat are rapidly 

 reduced ; and pieces of fibrine weighing several grains dissolve 

 .and totally disappear in two or three days. With cartilage the 

 action is most remarkable of all ; lumps of this weighing 8 or 

 10 grains are half gelatinised in twenty-four hours, and in three 

 days tlie whole mass is greatly diminished, and reduced to a 

 clear transparent jelly. After drying some cartilage in the open 

 air for a week, and placing it in an unopened but fully formed 

 pitcher of N. Rafflesiana, it was acted upon similarly and veiy 

 little slower. 



That this process, which is comparable to digestion, is not 

 wholly due to the fluid first secreted by the glands, appears to me 

 most probalile ; for I find that very little action takes place in 

 any of the substances placed in the fluid drawn from pitchers, 

 and put in glass tubes ; nor has any followed after six days' im- 

 mersion of cartilage or fibrine in pitchers of N. ampullaria placed 

 in a cold room ; whilst on transferring the cartilage from the 

 pitcher of A'', ainptdlaria in the cold room to one of Rafflesiaiia 

 in the stove, it was immediately acted upon. Comparing the 

 action of fibrine, meat, and cartilage placed in tubes of Nepenthes 

 fluid, with others in tubes of distilled water, I observed that their 

 disintegration is three times more rapid in the fluid ; but this 

 disintegration is wholly different from that effected by immersion 

 in the fluid of the pitcher of a living plant. 



In the case of small portions of meat, \ to 2 grains, all seem to 

 be absorbed ; but with 8 to to grains of cartilage it is not so — a 

 certain portion disappears, the rest remains as a transparent 

 jelly, and finally becomes putrid, but not till after many days. 

 Insects appear to be acted upon somewhat differently, for after 

 several days' immersion of a large piece of cartilage I found that 

 a good-sized cockroach, which had followed the cartilage and was 

 drowned for his temerity, in two days became putrid. In re- 

 moving the cockroach the cartilage remained inodorous for many 

 days. In this case no doubt the antiseptic fluid had permeated 

 the tissue of the cartilage, whilst enough did not remain to pene- 

 trate file chitinous hard covering of the insect, which conse- 

 quently decomposed. 



In the case of cartilage placed in fluid taken from the pitcher 

 — it becomes putrid, but not so soon as if placed in distilled 

 water. 



From the above observations it would appear probable that a 

 substance acting as pepsine is given olT from the inner wall of 

 the pitcher, but chiefly after placing animal matter in the acid 

 fluid ; but whether this active agent flows from the glands or 

 from the cellular tissue in which they are imbedded, I have no 

 evidence to show. 



I have here not alluded to the action of these animal matters 

 in the cells of the glands, which is, as has been observed by Mr. 

 Darwin in Drosera, to bring about remarkable changes in their 

 protoplasm, ending in their discoloration. Not only is there 

 aggregation of the protoplasm in the gland-cells, but the walls 

 of the cells themselves become discoloured, and the glandular 

 surface of the pitcher that at first was of a uniform green, 

 becomes covered with innumerable brown specks (which are the 

 discoloured glands). After the function of the glands is ex- 

 hausted, the fluid evaporates, and the pitcher slowly withers. 



At this stage I am obliged to leave this interesting investiga- 

 tion. That Nepenthes possesses a true digestive process such as 

 has been proved in the case of Drosera, Diona:a, and Pinguicula, 

 cannot be doubted. This process, however, takes place in a 

 fluid which deprives us of the power of following it further by 

 direct observation. We cannot here witness the pouring out of 

 the digestive fluid ; we must assume its presence and nature 

 from the behaviour of the animal matter placed in the fluid in 

 the pitcher. From certain characters of the cellular tissues of 

 the interior walls of the pitcher, I am disposed to think that it 

 takes little part in the processes of either digestion or assimila- 

 tion, and that these, as well as the pouring out of the acid fluid, 

 are all functions of the glands. 



In what I have said I have described the most striking in- 

 stances of plants which seem to invert the order of nature, and 

 to draw their nutriment — in part, at least — from the animal 

 kingdom, which it is often held to be the function of the vege- 

 table kingdom to sustain. 



I might have added some additional cases to those I have 

 already dwelt upon. Probably, too, there are others still un- 

 known to science, or whose habits have not yet been detected. 

 Delpino, for example, has suggested that a plant, first described 

 by myself in the Botany of the Antarctic Voyage, Caltha dionaa- 

 folia, is so analogous in the structure of its leaves to Diona:a, 

 that it is diflScult to resist the conviction that its structure also is 

 adapted for the capture of small insects. 



But the problem that forces itself upon our attention is, How 

 does it come to pass that these singular aberrations from the 

 otherwise uniform order of vegetable 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 — as we may do for a moment — 

 the nature of ordinary vegetable nutrition. Vegetation, as we 

 see it everywhere, is distinguished by its green colour, which we 

 know depends on a peculiar substance called chlorophyll, a sub- 

 stance which has the singular property of attracting to itself the 

 carbonic acid gas which is present in minute quantities in the 

 atmosphere, of partly decomposing it, so far as to set free a 

 portion of its oxygen, and of recombining it with the elements 

 of water, to form those substances, such as starch, cellulose, 

 and sugar, out of which the framework of the plant is con- 

 structed. 



But, besides these processes, the roots take up certain matters 

 from the soU. 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 nitrates and salts of 

 ammonia in minute quantities from the ground, and from these 

 they build up with starch, or some analogous material, albumin- 

 oids or protein compounds, necessarj' for the sustentation and 

 growth of protoplasm. 



At first sight nothing can be more unlike this than a Dionrea 

 or a Nepenthes capturing insects, pouring out a digestive fluid 

 upon them, and absorbing the albuminoids of the animal, in a 

 form probably directly capable of appropriation for their own 

 nutrition. Yet there is something 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 seedling lies between masses of this, and is in 

 contact with it ; and as the warmth and moisture of germination 

 set up changes which bring about the liquefaction of the contents 

 of the endosperm and the embryo absorbs them, it 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 carnivorous plants do later in life. 



That this is not a merely fanciful way of regarding the relation 

 of the embryo to the endosperm, is proved by the ingenious 

 experiments of Van Tieghem, who has succeeded in substituting 

 for the real, an artificial endosperm, consisting of appropriate 

 nutritive matters. Except that the embryo has its food given to 

 it in a manner which needs no digestion — a proper concession to 

 its infantine state — the analogy here with the mature plants 

 which feed on organic food seems to be complete. 



But we are beginning also to recognise the fact that there 

 are a large number of flowering plants that pass through 

 their lives without ever doing a stroke of the work that green 

 plants do. These have been called Saprophytes. Monotropra, the 

 cuiious bird's nest .orchis {Nectda iddus-avis), Zpipogium, and 

 Corallorhiza are instances of British plants which nourish them- 

 selves by absorbing the partially decomposed materials of other 

 plants, in the shady or marshy places which they inhabit. They 

 reconstitute these products of organic decomposition, and build 

 them up once more into an organism. It is curious to notice, 

 however, that the tissues of Neottia still contain chlorophyll in 

 a nascent though useless state, and that if a plant of it be im- 

 mersed in boiling water, the characteristic green colour reveals 

 itself. 



Epipogium and Corallorhiza have lost their proper absorbent 

 organs ; they are destitute of roots, and take in their food by the 

 surfaces of their underground stem structures. 



