No. 6.] HOOKER — CARNIVOROUS HABITS OF PLANTS. 369 



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 por- 

 tion 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 constructed. 



But, besides these processes, 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. Thev withanw nitrates and salts of 

 ammonia in minute quantities iVom t!ie ground, and from these 

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

 oids or protein compounds, necessary for the susteutation and 

 growth of protoplasm. 



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

 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 in- 

 fluence 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 

 efifect 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 ex- 

 periments 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 

 Vol. VII. Y No. 6. 



