No. 6.] HOOKER — CARNIVOROUS HABITS OF PLANTS. 371 



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 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 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 the viscid secretion of such a gland, 

 and to have perished there, being acted upon by those acid 

 secretions that abound in these and most other plants. The 

 subsequent difterentiation of the secreting organs of the pitcher 

 into aqueous, saccharine, and acid, would folio wj^an'pwssit 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 appre- 

 hension, transcend in wonder and interest those of evolution and 

 the origin of species. 



Delpino has recorded the fact that the spathe of Alocasia 

 secretes an acid fluid which destroys the slugs that visit it, and 

 which he believes subserves its fertilisation. Here any process 

 of nutrition can only be purely 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 sub- 

 stances with which they came in contact. Thus the acid secre- 

 tions of roots were found by Sachs to corrode polished marble 

 surfaces with which they came in contact, and thus to favour the 

 absorption of mineral matter. 



The solution of albuminoid substances requires, however, 

 besides a suitable acid, the presence of some other albuminoid 

 substance analogous to pepsine. Such substances, however, are 

 frequent in plants. Besides the well-known diastase, which con- 

 verts the starch of malt into sugar, there are other instances in 

 the synaptase which determines the formation of hydrocyanic 

 acid from emulsine, and the myrosin which similarly induces the 

 formation of oil of mustard. We need not wonder, then, if the 

 fluid secreted by a plant should prove to possess the ingredients 

 necessary for the digestion of insoluble animal matters. 



These remarks will, I hope, lead you to see, that though the 

 processes of plant nutrition are in general extremely difierent 



