RESERVE MATERIALS OF PLANTS. 113 



which there can be no doubt, we find many others the 

 function of which is still a matter of controversy. Such 

 bodies as tannin and phloroglucin are of fairly widespread 

 occurrence and much is to be said both for and against their 

 nutritive value. The vast number of alkaloidal matters 

 offer a further opportunity for discussion, some facts in 

 their history appearing to point to their possessing, at any 

 rate, some importance in nutrition in particular cases. 

 Lastly, we find in many plants small accumulations of 

 mineral matter often associated with proteid deposits, 

 though sometimes occurring separately, on which still much 

 remains to be said. 



In discussing the meaning- of these various bodies, the 

 peculiar relation of proteid substances to living protoplasm 

 indicates their primary importance and they necessarily 

 claim first attention. They are easily isolated, occurring as 

 they do in large quantities in many seeds ; and from their 

 being found generally without a very large admixture of 

 other bodies they offer a fairly easy task to the analyst. 

 In most works on vegetable physiology they are frequently 

 spoken of in a general way under the name of aleurone, or 

 aleurone grains. A section of a seed containing them 

 shows them usually as rounded or oval bodies, sometimes 

 presenting no particular structure, sometimes as containing 

 crystalloid bodies and generally a small aggregation of 

 mineral matter, which is usually a complex phosphate. Occa- 

 sionally, as in the potato, they have the appearance of a 

 cubical crystal, when the term aleurone grain is abandoned 

 for crystalloid. Their original appearance in the cells 

 in the seed has been investigated by several authors. 

 Pfeffer ( 1) published in 1872 the first observations on record 

 on this point. In his paper he attributes their first forma- 

 tion to the influence of the mineral constituent with which 

 they are associated. The latter, usually either minute crys- 

 tals of oxalate of calcium, or amorphous collections of the 

 double phosphate of calcium and magnesium, can first be 

 detected in the cell sap of the vacuole of the cell, and some 

 peculiar attraction causes the proteid matter to accumulate 



round them and enclose them in its substance. As the seed 



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