Chapter XV 



-171 



Origin of Vacuoles 



tion take on the appearance of solid, spherical, very refractive 

 bodies. These bodies can, by crushing, be expelled from the cell 

 and then will not take up neutral red unless they have been im- 

 mersed in water for a long time. 



The vacuoles are thus transformed into bodies of protein nature 

 whose dimensions are variable. They are very small in some cells 

 and very large in others. They are aleurone grains and are formed 

 by the solidification of the protein contained in solution in the 

 vacuole. As a result of losing water, a grain of protein has there- 

 fore been substituted for a vacuole. It is not astonishing, then, to 



Fig. 118. — Ricinus. Endosperm. 1, young cell, starch (A) 

 forms in chondriconts. 2, just before maturation; starch is 

 absorbed, the large vacuole is fragmented into small vacuoles con- 

 taining protein crystals (C) and protein precipitates (P). 3, oil 

 globules (H) blackened by osmic acid, protein crystals (P). 4, 

 detail of (3). 5, dormant seed; A, aleurone grain, G, globoid. 

 6, during germination of the seed; aleurone grains (P) beginning 

 to dissolve. M, chondriosomes. 1, 2, 5, 6, Regaud's method. 3, 4, 

 Meves* method. 



find along with the protein in these vacuoles, inclusions of phytin 

 and crystals of calcium oxalate, products encountered in many 

 vacuoles. Some aleurone grains may even contain oxyflavanol pig- 

 ments or anthocyanin. Investigations of Speiss and Chaze have 

 shown that aleurone grains of some varieties of maize contain an 

 anthocyanin pigment which gives them their characteristic black 

 coloration. At first red, this pigment appears in the vacuoles which 

 will later be transformed into aleurone grains, then remains ab- 

 sorbed by the protein of which the aleurone grain is composed. At 

 germination, when the aleurone grains are again transformed into 

 vacuoles, the anthocyanin pigment changes to red. Furthermore 

 Chaze has found oxyflavanol pigments in the yellow or white ker- 



