RESERVE MATERIALS OF PLANTS. 117 



the observations of Rendle, and seems rather opposed to 

 his theory of their mechanical deposition. The formation 

 begins late while the cells are a little short of their mature 

 condition and the grains appear first at the periphery of the 

 cells against the cell walls ; that is, in the limiting layer of 

 the protoplasm, and not, as a mechanical hypothesis would 

 suggest, in the vacuole of the cell. After their first appear- 

 ance they grow rapidly, and vacuoles form in their interior. 

 The grains so appear to have a definite structure, consisting 

 of a firm framework, enclosing within its meshes a peculiar 

 sap, rich in various constituents of which proteid matter 

 forms the chief part. The wall, or meshwork, is of different 

 composition, being insoluble in water. The sap in its 

 meshes is replaced as the seed ripens by proteid matter 

 alone, except that organic acids, galactine, etc., may be 

 detected in the latter in small quantity. 



Belzung's work was carried out on leguminous seeds, 

 chiefly the haricot bean, the common bean, the pea, the 

 lupin and the broom. 



In weighing the value of these several hypotheses as to 

 aleurone grain formation and attempting to decide whether 

 it is a vital process or no, it is clear that we have to take 

 into account the fact that there is a copious accumulation of 

 proteid matter in the cells as the seed is maturing. The 

 appearance of the grains can be explained in two ways. 

 Either they are formed in consequence of the transport of 

 proteid in solution to the cells in such a condition as to be 

 readily precipitated by the organic acids, etc., formed there, 

 or they must be constructed from other plastic materials 

 at the place where they are deposited. If they are trans- 

 ported in proteid form they must travel either as peptone or 

 in the condition in which Belzung suggests they exist in the 

 cell antecedently to their precipitation, that is, either as 

 albuminates of an alkali metal, or in some state of solution 

 with the phosphates in the sap. It is difficult to entertain 

 either view ; peptone is the only form of proteid which is at 

 all easily diffusible through membranes, such as cell walls ; 

 but peptone has not been found in the cells during or before 

 the deposition of the grains, nor would peptone be trans- 



