COMPOSITION OF ALEUEONE GRAINS 451 



form. In many seeds they are deposited in the form of grains of 

 complex nature, and sometimes of elaborate structure. Grains of 

 proteid material are known as aleurone grains. Sometimes they 

 are small, rounded and structureless, as in the Pea {fig. 1190). 

 In other seeds, as in the castor-oil plant, they are much larger, 

 of rounded or ovoid form, and contain a crystal of proteid matter, 

 which often occupies nearly their whole substance [fig. 1191). 

 This has been called a crystalloid. There is in such cases also a 

 small aggregation of mineral matter which lies close to the 

 crystal. This is known as a globoid, and consists of a double 

 phosphate of calcium and magnesium. 



The proteids of the aleurone grain are generally mixtures of 



Fig. 1191. 



_y/. 



Fi'j. 1190. Cells of a very thin section through a cot3'ledon of the embryo in 

 a ripe seed of tlie common Pea {Pisinn sativum), a, a. Aleurone grains. 



St. Starch granules. /,«. Intercellular spaces. (After Sachs. ) Fig. \\^\. 



Cell from the endosperm or albumen of the seed oi the Castor-oil plant 

 {Riciiius comitvinis) in dilute glycerine, showing large transparent proteid 

 or aleurone grains, with crystalloids and globoids embedded in them. 

 (After Sachs.) 



globulins and albumoses, the latter being least in quantity. If 

 a section of a castor-oil seed from which the oil has been 

 removed, be irrigated with water, a part of the outer substance 

 of the grain is dissolved, leaving still an ovoid body, in which 

 the crystal, or crystalloid, can be seen. The part dissolved 

 consists of the albumose, which is soluble in water. If the 

 section be then irrigated with a ten per cent, solution of common 

 salt, the body of the grain dissolves. This is composed of a 

 particular globulin. The crystalloid will dissolve if it be 

 treated with a saturated solution of the same salt, showing it to 

 be made up of another globulin. 



Other aleurone grains show other peculiarities of solubility, 



G G 2 



