THE RESERVE MATERIALS OF PLANTS. 73 



comparative analyses taken at considerable intervals of time 

 that the proteids change after deposition. Whether the 

 changes only go on during- a comparatively short period, 

 corresponding to the ripening of the seed, or whether they 

 are prolonged till the power of germination is lost, remains 

 an open question. 



Some experiments bearing on this point were published 

 by Acton (21) two years ago, analyses having been made 

 of a sample of new wheat, and of another of wheat grown 

 upon the same land thirty years before, during the 

 interval it having been kept in the stack. Too much 

 stress must of course not be laid upon the experiment, as it 

 is probable that the samples did not exactly correspond. 

 The results of the analyses showed that the old wheat had 

 lost nearly half its water ; that compared with the new 

 wheat the proteids insoluble in water were as 4/3 : yi ; 

 those soluble in water 3*9: 1*2. Asparagin, which was 

 absent from the new wheat, was present in the old sample 

 to the extent of "8 per cent. The tendency during ripen- 

 ing, or subsequently, was therefore in the direction of 

 forming soluble and diffusible bodies from others which 

 were neither. During the interval the old wheat had lost 

 the power of germinating, and contained no enzyme, 

 though this was present in the new sample. 



The nitrogenous reserve materials which are found in 

 form of amides are probably almost entirely confined to the 

 circulating supply. A few are found in resting seeds, but 

 they are more readily detected after germination has begun, 

 and must therefore be looked upon rather as intermediate 

 products. Being as a rule soluble in the cell sap, they are 

 with difficulty detected. Belzung (22) has succeeded by a 

 new method in ascertaining their presence. He places 

 fresh sections of the living seed in strong glycerine.; after 

 the lapse of a variable time, ranging from a few hours to 

 two or three days, the amides crystallise out in their 

 characteristic forms. The method is sufficiently accurate 

 to yield a good idea of the relative amounts present. It 

 needs supplementing of course by the extraction of the 

 amides from considerable quantities of the seeds and a sub- 



