PROPORTION OF OIL IN DIFFERENT SEEDS. 529 



which differs in its properties from the gluten and albumen of the seeds 

 of the corn-bearing plants, and has much resemblance to the curd of 

 milk. Besides their fattening properties, therefore — which these seeds 

 probably owe in a great measure to the oil they contain — this peculiar 

 albuminous matter ought to render them very nourishing also ; — capable 

 of promoting the growth of the growing, and of sustaining the strength 

 of the matured, animal. 



The quantity of oil contained in different seeds of this class, and even 

 in the same species of seed when raised in different circumstances, is 

 very variable. These facts will appear from the following table, which 

 represents the proportions of oil that have been found in 100 lbs. of some 

 of the more common seeds : — 



Oil per cent. 



Line seed 11 to 22 



Hemp seed 14 to 25 



Rape seed 40 to 70 



Poppy seed . . . . 36 to 53 

 White mustard do. . . 36 to 38 

 Black do. do. . . 15 

 Swedish turnip do. . . 34 



It seems to be a provision of nature, that the seeds of nearly all plants 

 should contain a greater or less proportion of oil, which is lodged for the 

 most part in, or immediately beneath, the husk, and, among other pur- 

 poses, may be intended to aid in preserving the seed. We shall here- 

 after «ee that this oily constituent is of much importance also to the prac- 

 tical agriculturist. 



§ 26. General differences in composition among the different kinds of 

 vegetable food. 



It may be useful shortly to recapitulate the leading differences in 

 chemical constitution which exist among the different kinds of vegetable 

 food to which I have directed your attention in the present lecture. 



We have seen that each of the varieties of food contains a greater or 

 less proportion of three different classes of chemical substances — an 

 organic substance containing nitrogen, an organic . substance containing 

 no nitrogen, and an in-organic substance. But it is interesting to mark 

 how in each class of those vegetable products which we gather from the 

 earth for our sustenance, the organic substances vary either in composition 

 or in chemical characters, while the inorganic matter alters also either in 

 kind or quantity. Thus — 



1°. In the seeds of the com plants — wheat, oats, &c. — the predomi- 

 nating ingredient is starch, in connection with a considerable proportion 

 of gluten, and a small quantity of saline matter consisting chiefly of the 

 phosphates of potash and of magnesia, and in the case of barley of a 

 considerable proportion of lime. 



2°. In the seeds of leguminous plants — the pea, the bean, the vetch, 

 6cc. — starch is still the predominating ingredient, but it is connected with 

 a large quantity of legumin, and with a greater proportion of inorganic 

 Blatter — in which phosphate of lime also is more abundant. 



3°. In the oil-beanng seeds — those of hemp, lint, dec — oil is often the 



