ERGASTIC SUBSTANCES 101 



with them. The eggs of gymnosperms may contain large globules or 

 shapeless masses of albuminous reserves. Refractive "metachromatic 

 corpuscles," composed of metachromatin, a nucleic acid compound, may 

 occur in the vacuoles and cytoplasm of certain algae, fungi, and Protozoa 

 (Guilliermond) ; these are what A. Meyer calls volutin globules. In 

 Meyer's opinion both chondriosomes and nucleoli are ergastic protein 

 masses. 



Protein crystals occur widely in both plants and animals. They con- 

 sist chiefly of albumins and globulins and may be found in the cytoplasm, 

 plastids, nucleus, or vacuoles. ^^ The best known albumin crystals are 

 those found in aleurone grains, which are ordinarily made up of both 

 crystalline and amorphous protein elements. These grains occur in the 

 endosperm, embryo, and perisperm of ripe seeds, being 

 especially prevalent in such oily seeds as those of 

 Ricinus, Juglans, and Bertholletia. In maize and wheat 

 kernels they lie in the outermost layer of endosperm 

 cells. Aleurone grains differ considerably in color, 

 form, and structure. ^^ In many cases {e.g.,Pisum) the 

 grain consists only of an amorphous substance. In ^ig "52 — Aieu- 

 other cases this ground substance encloses a rounded rone grain from en- 

 "globoid" (in grasses), a crystal of calcium oxalate (in nuT^^m°lunlT. 

 certain Umbelliferse), or a large angular albuminous (After A. Meyer, 

 "crystalloid." The well-known aleurone grain of the 

 deeply lying endosperm cells of Ricinus consists of a protein ground sub- 

 stance, a crystalloid, and a globoid composed of a double phosphate of 

 calcium and magnesium together with certain organic constituents 

 (Fig. 52). 



The development of the aleurone grain has been repeatedly studied, 

 especially in Ricinus. It now seems clear that the early investigators 

 (Maschke, Gris, Wakker) were correct in their statement that the grains 

 appear in vacuole-like cavities as the seed matures. They regarded these 

 cavities as actual sap vacuoles, a view which was again emphasized by 

 the Dangeards.'^'* According to this interpretation, the vacuolar material 

 passes through a reticular stage and breaks up into a number of small 

 vacuoles in which the gradually condensing constituents differentiate 

 as crystalloid, globoid, and ground mass. According to Mottier (1921), 

 aleurone formation involves the activity of permanent plastid primordia. 

 These aggregate in large numbers in the vacuole-like cavities, where their 

 combined products unite to form the aleurone grains. Vouk (1925) 



^2 Protein crystals are treated at length by Meyer (1920). For nuclear crystals, 

 see also Tischler (1921-1922) and W6ycicki (19296). 



"Hartig (1856), Maschke (1859), Gris (1864), Pfeffer (1872), Tschirch (1887), 

 Wakker (1888), Liidtke (1890), Guilliermond (1907a). 



" P. A. Dangeard (1919, 1920ac), P. Dangeard (1920, 1921a6c, 1922a, 1923a). 



