^4 MORPHOLOGY OF THE CELL, 



of the latter may be very small. Thus even in the castor-oil-plant and brazil-nut, 

 where the matrix appears to consist entirely of oily matter, the albuminous constituent 

 is quite discernible, as is shown in Fig. 48, D ; Pfeffer succeeded most readily 

 by extracting with an alcoholic solution of corrosive sublimate, and then colouring 

 with anilin-blue dissolved in water. The matrix may be considered as the proto- 

 plasm-mass of the cell, in which the water is replaced on drying by oil. But in 

 addition it contains not only insoluble proteids, but other substances soluble in 

 water rendered alkaline by potash. This composition of the matrix, together with 

 the solubility of the amorphous mass of the aleurone-grains in water, are the cause 

 of the complete loss of form which the cell-contents of oily seeds immediately 

 undergo in water, as shown in sections under the microscope. In order to recognise 

 their structure it is necessary to place fresh sections in undiluted glycerin, alcoholic 

 solution of corrosive sublimate, oil, or concentrated sulphuric acid. 



The oily matter may also separate from the matrix in crystals, as Pfeffer has 

 observed in the brazil-nut, Elaeis guineensis, and the nutmeg. 



To the above may be added, from Pfeffer's communication, some explanations con- 

 cerning the more difficult points. 



(a) The substance of the aleurone-grains always consists, to by far the greater extent, 

 of proteids, with which very small quantities of other vegetable substances are usually 

 or always mixed which are difficult of detection. All aleurone-grains are absolutely 

 insoluble in alcohol, ether, benzol, or chloroform ^ ; these reagents would dissolve oil 

 (alcohol dissolves also glucose), if it were present, and would consequently alter the 

 appearance of the grain. Some are insoluble in water {e.g. those oiCynoglossum officinale) ; 

 those soluble in water ^ yield with corrosive sublimate in absolute alcohol a mercury- 

 compound insoluble in water. Gum, pectinaceous substances, cane-sugar, and dextrin 

 do not, under this treatment, yield an insoluble compound. Of all widely distributed 

 vegetable substances, only proteids behave in this manner towards corrosive sublimate. 

 Boiling the mercury-compound with water reproduces a proteid insoluble in dilute acids 

 and alkalies. 



(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 between the grains, can be settled by calculation ; for if spheres 

 (the grains may be so regarded) are placed in an equal number of cubes forming 

 part of one great cube, 47-6 p. c. of the cavity remains unoccupied ; and if the 

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

 of the 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 oil in seeds which contain it by 

 the appearance presented by dry sections; if benzol is added, the matrix disappears, 

 while small quantities of proteids remain. With alcoholic tincture of alkanet the matrix 

 becomes of a deep blood-red colour if it contains a considerable amount of oil ; but 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 by alcohol, and the aleurone-grains then 

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



' That I formerly considered them soluble in ether, was the result, as Pfeffer showed, of the 

 containing a small quantity of water. 

 2 On the causes of the solubiUty in water see Pfeffer's treatise already cited. 



