GRAINS OF ALEURONE. ^^ 



which the best in this case is boiling the mercury-compound with water. The modifi- 

 cation of proteinaceous substance insoluble in dilute acids and alkalies is thus formed. 



(b) In proving that the aleurone-grains of oily seeds contain no oil, we have 

 already seen that it must be present in the matrix. The doubt which arises from the 

 first glance at sections of oily seeds, whether the great mass of oily matter can find space in 

 the interstices of the grains, can be settled by calculation ; for if spheres (the grains may 

 here be considered in this light) are so placed that they are enclosed in any number of 

 equal cubes forming part of one great cube, 47*6 p. c. of the cavity remains; and if the 

 spheres are distant from one another only about one-third of their radius, 697 p.c. ofthe 

 cavity is left, and this is more than is sufficient in oily seeds to take up the oily matter. 



Immediate proof can be given of the existence of the oil in seeds which contain a 

 certain amount of it by the appearance presented by the observation of dry sections ; if 

 benzol is then added the intermediate masses are seen to disappear, while small quanti- 

 ties of albuminoids always remain. Treated with alcoholic tincture of alkanet the 

 matrix becomes of a deep blood-red colour if it contains a considerable amount of 

 oil ; if the oily constituents of the seed are very small, the evidence cannot be obtained 

 in this manner. 



If the oil is extracted from the sections of seeds by alcohol, and the grains of proteine 

 then removed by solution of potash, a net-work remains behind in which the grains are 

 replaced by cavities; on addition of acetic acid and iodine the net-work assumes a 

 yellow-brown colour (Fig. 49, JS; 50, D). In most seeds this net-work is very beautiful, 

 comparable, to a certain extent, to parenchymatous tissue ; in extremely oily seeds it 

 often breaks up into fragments, the nucleus lying in it like a shrivelled ball. The 

 threads of the net-work are composed of the insoluble proteinaceous materials of the 

 matrix and of the enveloping membranes of the grains of proteine ; although a net-work 

 may exist without the latter if grains have disappeared. 



(c) The Crystalloids of the grains of aleurone are, as has been said, insoluble in water ; 

 they may therefore easily be isolated by treatment of fresh sections with water, the 

 amorphous masses of aleurone dissolving, and the rest of the cell-contents being de- 

 stroyed ; they then show all the reactions and the different forms of the crystalloids 

 mentioned in sect. 7. But that they consist of two proteinaceous substances, and grow 

 from within by intussusception, Pfeffer thinks he has good grounds for doubting. 



(d) If sections of the endosperm of the peony are treated with alcohol containing a 

 small quantity of sulphuric acid, and if, after washing, they are placed in water, the sub- 

 stance of the grains of aleurone (not containing crystalloids) is seen to be distinctly 

 stratified ; but only a few firm and soft layers occur, the inner part of the mass is 

 amorphous. PfeflTer's work should also be consulted here. 



(e) The De'velopment of the grains of aleurone is thus described by the investigator 

 already so often named. — Their formation commences when the seeds attain the last 

 condition of ripeness and the funiculus begins to become sapless ; in the very turbid 

 emulsion which now fills the cells, the enclosed substances, especially the globoids, are 

 already formed ; they are, even if not quite perfect, neaWy fully developed. Then, as 

 the seed loses its water, the formation of mucilaginous masses commences, consisting of 

 proteinaceous substances, which mostly already surround enclosed substances ; these 

 mucilaginous bodies, usually nearly globular, continue to grow; their mutual distance 

 thus decreases, and at -last the separation is complete ; the grains of proteine, still con- 

 sisting of mucilaginous substance, are separated from the still turbid matrix, which be- 

 comes clearer and clearer, while the seed becomes drier. Thus the previously spherical 

 or ellipsoidal grains become more or less polyhedral, especially, as may easily be observed, 

 in a few oily seeds which have generally bilt little matrix {e.g. Lupinus). 



While the formation of the grains of aleurone is beginning, the protoplasmic mass of 

 the cell is only to be detected with difficulty in the turbid cell-contents ; yet, on remov- 

 ing the oily matter by alcohol, it may be shown that it is present in the normal form ; 

 sometimes in the copious matrix of some seeds the dried strings of protoplasm may be 



