230 



NATURE 



\7tily 22, 1875 



flexibility ; the collar itself being furnished with similar 

 but two-armed bodies. 



The use of these bladders is not merely, like the air- 

 bladders of Fticns, to support the plant in the water ; they 

 are employed to capture small aquatic insects and other 

 animals, which they do on a large scale. What it is that 

 attracts the animals to enter the bladders is at present 

 unknown ; but, having once entered by pressing down the 

 valve, escape is almost impossible ; they sometimes get 

 closely wedged between the valve and the collar, and thus 

 miserably perish. But the most mysterious part of the 

 structure of Utricularia is that this beautiful and compli- 

 cated arrangement for capturing prey is not accompanied 

 by any correspondingly perfect arrangement for its diges- 

 tion. No secretion whctever has been observed to exude 

 from either the glands or the quadrifid processes ; pieces 

 of meat and albumen inserted within the bladders re- 

 mained absolutely unchanged for three days ; and it is 

 only when the bodies of the captured animals begin to 

 decay that the products of decomposition are slowly 

 absorbed by the quadrifid processes ; and of even this 

 fact the evidence can only be said to be indirect, depend- 

 ing on a change observed in the appearance of the proto- 

 plasmic contents of the cells of the quadrifids and of the 

 glands on the valve and bifids on the collar, similar to 

 that which takes place in the tentacles of Drosera during 

 digestion. 



The above description is taken from the rare Utricu- 

 laria iicglecta, the species first observed by Mr. Darwin ; 

 the phenomena are essentially the same in the other 

 British forms. An epiphytic South American species, 

 U. mo7itana, bears bladders of a similar structure in all 

 essential points, which capture a quantity of minute 

 animals. This species is also furnished on its rhizomes 

 with a number of small tubers, which appear to serve as 

 reservoirs of water during the dry season. Several other 

 species were examined, including the Brazilian U. ncliim- 

 bifolia, found only in a very remarkable habitat, floating 

 on the water which collects in the bottom of the leaves of 

 a large Tillandsia that inhabits abundantly an arid rocky 

 part of the Organ Mountains at an elevation of about 

 5,000 feet above the level of the sea. In addition to the 

 ordinary propagation by seed, this plant is said to put out 

 runners which are " always found directing themselves 

 towards the nearest Tillandsia, when they insert their 

 points into the water and give origin to a new plant, 

 which in its turn sends out another shoot." 



It is very curious and suggestive to compare and con- 

 trast the contrivances displayed in the two genera, 

 Pinguicula and Utricularia, belonging to the same 

 natural order. In the latter case we have a most elabo- 

 rate and perfect contrivance for capturing insects, remind- 

 ing one of what Mr. Darwin describes elsewhere as 

 '■' transcending in an incomparable degree the contri- 

 vances and adaptations which the most fertile imagination 

 of the most imaginative man could suggest;" but, when 

 the insects are once captured, there is no contrivance for 

 hastening the decay of their tissues, or anything com- 

 parable to animal digestion. In Pinguicula, on the other 

 hand, the digestive apparatus is most complete ; but 

 there is no means whatever of capturing insects, except 

 the very perfectness of the digestive substance itself, the 

 extremely viscid nature of the secretion from the glands- 



What was the primitive form which has developed into 

 such very diverse structures in these nearly-allied genera ? 

 Here we have a problem for the evolutionist to work out ; 

 and another for the natural selectionist — what benefit to 

 the plant were these contrivances in their elementary 

 rudimentary stage ? — a consideration necessary to the 

 hypothesis of their having been produced by the action of 

 selection. There is a difficulty in conjecturing what use 

 a digestive fluid can have been to the Pinguicula before 

 it attained a degree of perfection sufficient to capture 

 insects, or rudimentary bladders to the Utricularia, seeing 

 they were not endowed with the power of digestion. 



The last genus examined by Mr. Darwin belongs also 

 to the Lentibulariaceae, the Brazilian Genlisea. It is also 

 utriculiferous ; but the bladders are of a very different 

 nature to those of Utricularia, being simply hollow 

 cavities in the very long petiole or narrow part of the 

 lamina of certain leaves specialised for this purpose. The 

 bladders are not more than g>gth of an inch in diameter, 

 and are surmounted by a long tube fifteen times as long 

 and only -^l^ inch in diameter, which branches at the 

 extremity into two arms coiled in a spiral manner. Very 

 little is known of the habits of the plant, of which only 

 dried specimens have been examined in this country. It 

 is probable that insects creep down the long tube into the 

 bladders, where their remains have been found, and 

 there perish ; but whether there is any process of diges- 

 tion is unknown. The escape of insects once captured is 

 prevented, not by a valve, as in Utricularia, but by rows 

 of long thin hairs pointing downwards and springing 

 from ridges which project from the inside of the tube, as 

 shown in fig. 10. The inside of the utricle and of the 

 neck are furnished in addition with a number of qua- 

 drifid processes, also represented in the figure, to which the 

 function of absorption is ascribed, and which are com- 

 pared to the " quadrifids " cf Urticularia. The drawing 

 of these processes, more than the description, reminds us 

 strongly of certain structures which occur in the leaves of 

 Drosera and Pinguicula, and which we do not find 

 referred to in the present volume ; nor do we know of 

 any description of them elsewhere. Imbedded in the 

 tissue of the leaf of both genera — in the former case often 

 beneath the tentacles — are a number of bodies consisting 

 of four cells and filled with a brown matter; and we 

 cannot but think that attention directed to these bodies 

 may be rewarded by a further insight into the processes 

 of digestion and absorption. They are quite distinct from 

 the papilte described by Mr. Darwin in the case of 

 Drosera. We have seen also analogous structures repre- 

 sented in drawings by Dr. Hooker of cither Nepenthes or 

 Sarracotia ; and similar bodies occur in the leaves of 

 some water-plants, as Callitriche, to which we are not 

 aware that any function has been assigned. 



We have attempted in this notice to introduce our 

 readers only to some of the salient points of Mr. Darwin's 

 researches ; and cannot hope to give any idea of the 

 unwearying labour, the precision of the experiments, and 

 the wealth of illustration, for which we must refer all 

 interested in the subject to the volume itself. The novelty 

 of the results arrived at does not lie in the fact of plants 

 being found to feed on organic matter whether animal or 

 vegetable ; physiologists [have long been famihar with 

 this povrer in theease of parasites and saprophytes, the 



