ALEURONE-GRAINS. 55 



by cavities ; with acetic acid and iodine the net-work assumes a yellow-brown colour 

 (Fig. 47, B\ 48 D). In most seeds this net-work is very beautiful and comparable to 

 a 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 proteids of the matrix and of the enveloping membranes of the aleurone- 

 grains; although the net-work may exist without the latter if the grains have fallen 

 from their places. 



(c) The Crystalloids of the aleurone-grains are insoluble in water ; they may therefore 

 easily be isolated by treatment of sections with water, the amorphous portions of the 

 grains dissolving, and any residue of cell-contents being destroyed ; they then show all 

 the reactions and the different forms of the crystalloids mentioned in Sect. 7. But 

 that they consist of two proteids and grow by intussusception Pfeifer thinks very 

 doubtful. 



(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 

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

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

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



(e) The De'velopment of the aleurone-grains is thus described by Pfeflfer. — Their 

 formation does not commence till the seeds* have attained their last condition of 

 ripeness and the funiculus begins to dry up ; in the turbid emulsion which now fills 

 the cells, the enclosed substances, especially the globoids, are already formed, but 

 not fully developed. As the seed loses water, the formation of mucilaginous proteid- 

 masses commences, mostly surrounding enclosed substances ; these mucilaginous bodies, 

 usually nearly globular, grow, their mutual distance thus decreases, and at last their 

 differentiation is complete; the aleurone-grains, still consisting of mucilaginous sub- 

 stance, are distinctly separated from the still turbid matrix, which becomes clearer 

 and clearer as the seed dries. The previously spherical or ellipsoidal grains become 

 more or less polyhedral, especially in oily seeds which have but little matrix {e.g. 

 Lupinus). 



While the formation of the aleurone-grains is beginning, the protoplasm of the cell is 

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

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

 times in the copious matrix of some seeds the dried threads of protoplasm may 

 still be seen. In Lupinus luteus the crystal of calcium oxalate, which is after- 

 wards enclosed by the largest grain, is already present before the formation of the 

 aleurone-grains. Pfeffer was able to follow the development of the grains with remark- 

 able ease in the peony ; in this case the seed, even when it has attained its full size, is 

 entirely filled with large starch-grains, which become changed into oil only when fully 

 ripe. The starch is not always, however, completely changed into oily matter. If the 

 starch-grains in the seeds of the peony were not completely transformed, and the inter- 

 mediate mass, almost devoid of oily matter but very rich in proteids, formed very 

 small aleurone-grains, we should have what does actually occur in Phaseolus and in other 

 seeds extremely rich in starch. There are, however, also seeds in which aleurone- and 

 starch-grains occur in nearly equal quantities, but then always associated with oily 

 matter. 



No conclusion as to the manner of growth can be deduced from the turbid 

 condition of the cell-contents and the softness of the growing aleurone-grains. 

 Nevertheless it can mostly be affirmed with regard to ripe grains, that they are softer 

 towards the inside, and that, consequently, on the application of very dilute reagents, 

 they dissolve from within outwards. Different facts appear, nevertheless, to show that 

 no growth takes place by intussusception, as is the case with starch-grains. The 

 origin of aleurone-grains is simply a dissociation, which arises from loss of water 

 by the seed; and, on germination, the original cell-contents are again more or less 



