ALEURONE GRAINS. 33 



stance lies between them, more ground substance can be observed 

 against the. walls of the cells. The walls of the cells are very 

 strongly thickened and pitted, a structure which we shall, how- 

 ever, study later upon a more favourable object. In iodine- 

 glycerine the grains take a beautiful golden-yellow colour ; in 

 alcoholic borax-carmine they soon become red. 



Aleurone Grains and Crystalloids of Ricinus. In the next 

 place we will take the seed of the castor-oil plant (Ricinus com- 

 munis), from which we first remove the shell-like testa, then cut 

 the kernel across, and make preparations from it just as above. 

 The tissue of the endosperm is capital material to cut ; it contains 

 very much fat oil, and need not be moistened. We will first 

 examine sections in olive oil. The aleurone grains distributed in 

 the cells of the endosperm appear in the form of small ovate 

 bodies (Fig. 13). The narrower end of the grain is marked by a 

 small rounded body, which 

 appears as if hollo w, be- 

 cause it is less highly re- 



fractive than the olive oil. *. "JBt ^| 



This body is called the 

 globoid ; it is mineral, and 

 it consists essentially of a 

 double phosphate of lime ^WBp- 



and magnesia. I he other ir^^ 



constituents of the grain FIG. 13. From the endosperm of Rwinus 

 d\\r\&\v pnlrmrlpce nr^ffir 'wnmunis. A, a cell of the endosperm with its 



appeal colourless, pretty contentS) viewed in water . B si ^ le aleurone 



highly refractive, occasion- grains seen in olive oil ; g, the globoid ; k, the 



, , protein crystal ( x 540). 



ally more or less angular. 



We examine other sections in water. The globoids of the 

 aleurone grains are now more highly refractive, and we can 

 definitely see that they are solid bodies (Fig. 13). Each 

 aleurone grain encloses one, rarely more, protein crystal, or 

 crystalloid. The aleurone grains are embedded in a ground 

 substance which is rich in oil. The water in which the sections 

 are lying soon begins to displace the oil from the ground sub- 

 stance ; this latter is gradually disorganised ; great masses of oil 

 collect upon and around the section. These in part cling to the 

 object and to the glass, and have an irregular form, in part lie free, 

 and then are spherical. Most of them appear turbid with numerous 

 vacuoles. If the microscope be adjusted to an optical section of such 

 an oil-drop, it appears bright grey, and is bounded by a narrow black 



3 



