TRANSACTIONS OF THE SECTIONS. 115 
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 Weottia still contain chlorophyl in a nascent though useless state, and 
that if a plant of it be immersed in boiling water the characteristic green colour 
reveals itself*. Zpipogium 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-structurest. 
The absolute difference 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 ie useful. It was long 
ago suggested that the receptacle formed by the connate leaves of Dipsacus might 
be an incipient organ of this kind {; and though no insectivorous habit has ever been 
brought home to that plant, the suggestion is not improbable. 
Linneus and, more lately, Baillon § have shown how a pitcher of Sarracenia may 
be regarded as a modification of a leaf of the Nymphea type. We may imagine 
such a leaf first becoming hollow, and allowing débris of different kinds to accu- 
mulate ; these would decompose, and a solution would be produced, some of the 
constituents 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 Sarracenia purpurea) the matter absorbed was merely the saline 
nutritive products of decomposition, such as ammoniacal salts. The act of di- 
gestion (that process by which soluble food is reduced without decomposition to a 
soluble form fitted for absorption) was doubtless subsequently acquired. 
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 consi- 
derable quantities ||; and the pitcher of Nepenthes is, as I have shown elsewhere ¥, 
only a gland of this kind enormously developed. May not, therefore, the wonderful 
pitchers and carnivorous habit of Nepenthes have both originated by natural selec- 
tion out of some 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 the viscid secretion of such a gland, and to have perished 
there. Delpino has recorded the fact that the spathe of Alocasia odora secretes an 
acid fluid which destroys the slugs that visit it, and which he believes subserves 
its fertilization**, Here any process of nutrition can only be secondary. But 
the fluids of plants are in the great majority of cases acid, and when exuded would 
be almost certain to bring about some solution in substances with which they came 
in contact. Thus the acid secretions of roots were found by Sachstf to corrode 
polished marble surfaces with which they came in contact, and thus to favour the 
absorption of mineral matter. The subsequent differentiation of the secreting organs 
of the pitcher into aqueous, saccharine, and acid would follow, part passu, with the 
evolution of the pitcher itself, according to those mysterious laws which result in the 
correlation of organs and functions throughout the kingdom of Nature, and which, in 
my apprehension, transcend in wonder and interest those of the origin of species. 
The solution of albuminoid substances requires, however, besides a suitable acid, 
the presence of some other albuminoid substance analogous to pepsine. Such sub- 
stances, however, are frequent in plants. Besides the well-known diastase, which 
converts the starch of malt into sugar, there are other instances—in the synaptase 
* Prillieux, Ann. des Sc. Nat. 5¢ sér. vol. xix. p. 108. 
+ Sachs’s ‘ Lehrbuch der Bot.’ 3rd ed. p. 629. 
+ Burnett, /.c. p. 287; Darwin, ‘Bot. Gard.’ pt.i. p.37; Kirby and Spence’s ‘Entomo- 
logy,’ 7th ed. p. 167. 
§ Adansonia, vol. ix. pp. 331 & 380. 
|| See Ann. & Mag. Nat. Hist. 1848, vol. i. p. 188, where a species of Caladium is said to 
have secreted half a pint of fluid from each leaf in the course of the night. 
{| Trans. Linn. Soe. vol. xxii. pp. 415-424. Substantially the same view of their origin 
appears to have been taken by Griffith, Posth. Papers, vol. ii. p. 77. 
** Loc, cit. p. 237. tt Lebrbuch der Botanik, 3rd ars 2 611. 
