508 
On the Food of Plants. 
able from the casein of animal milk by anv means physical or 
chemical, and still more strange to say, a})parenlly in the same 
state of combination, and associated with the same inorganic sub- 
stances, as in milk itself.* 
As may be imagined from such a statement, the proportion of 
gluten in the different kinds of grain and for food will determine^ 
to a great extent at least, their relative nutritious values. We 
shall see hereafter that this proportion varies considerably in the 
same grain grown under different circumstances, so that the study 
of these things has a direct and immediate bearing on the practice 
of agriculture. 
With respect to the inorganic constituents of plants. From the 
comparatively small quantity in which these matters occur, they 
have usually been regarded as adventitious, and accordingly 
neglected. We have reason to reject this idea, at least with re- 
gard to many of them ; Liebig has taken pains to show, princij)ally 
by the analyses of the ashes of certain woods made by M . Berthier, 
of the Ecole des Mines, that a certain number of inorganic 
matters, in particular quantities, are essential to the well-being 
of a plant ; and that although variations among them occur, they 
take place in a regular manner and according to a fixed law. 
Many of the now old ash-analyses of De Saussure lead to the 
same conclusion, which is also borne out by my own experiments 
described in the latter part of this essay. 
The subject of vegetable structure and physiology is so exten- 
sive and so complicated, and withal so little understood, that any- 
thing like an attempt at description of what is known of the 
anatomy and living functions of plants would be out of place. 
The following slight notice must suffice. 
In examining a plant, even from among those highest in the 
scale, we cannot avoid being struck by two things ; the total 
absence of "anything like the circulatory arrangement of the higher 
animals, and the want of a nervous system. It is no argument 
against this to bring forward the case of the numerous tubes 
which are found in some plants, formed, as is thought, of a mem- 
brane having a spiral fibre within, as these are admitted to termi- 
nate after a short course, and are never known to anastomose. 
The recently seen '• vessels of the latex" also are too obscure and 
too little known to form a good exception. With respect lo nervous 
energy, something like this seems to exist in the well-known sen- 
sitive plant : it is not contended that plants are entirely destitute 
of something of the kind, as the curious and opposite effects of 
narcotic and irritant poisons on them serve to show, and which 
indeed seems to be involved in the very idea of life of any de- 
* Annalen der Pharmacie, 39' 
1—143. 
