STARCH. 



47 



in concentrated glycerin; (3) concentrated potassic hydrate, 

 water being added afterwards. Permanent preparations of pro- 

 tein crystals can be made by first acting on the section with 

 mercuric chloride for a day or more, washing in water, staining 

 with eosin, and finally mounting in potassic acetate (101). 



The inorganic matters associated with the protein crystals 

 in protein grannies are either 

 (1) amorphous or globular con- 

 cretions of a double phosphate of 

 calcium and magnesium, known 

 as globoids, or (2) crystalline 

 clusters of calcic oxalate. 



The protein granules, espe- 19 21 



ciallv those which are most com- 



j 



plex in their composition, are also known as Aleurone grains. 



The protein crystals are generally termed crystalloids. 1 For an 



analytical classification of protein granules in seeds, see pages 



182 and 183. 



178. Starch, the principal form in which the elaborated food 



of plants is held in reserve, occurs as minute spheroidal or 



polyhedral granules. Under a suf- 

 ficiently high power, and with 

 proper management of the mirror 

 of the microscope, the single gran- 

 ules exhibit an appearance of 

 stratification which is sometimes 

 very distinct, but more commonly 

 obscure ; in the latter case dilute 

 chromic acid can be used to ren- 

 der the stratification plainer. The 



__ _ lavers of stratification are ar- 



V 



ranged around a point, - - often very eccentrically, as in potato 



1 The fact that protein crystals have, as a rule, less constancy in their angles 

 than inorganic crystals, taken together with the fact of their swelling when 

 immersed in water, has led authors to speak of them as crystalloids rather than 

 as crystals. But Famintzin has recently shown that certain crystalline forms 

 artificially produced obscure these distinctions, since they agree more closely in 

 some of their physical characters with organic structures than with ordinary 

 inorganic crystals (Ber. der deutsch. bot. Gesellsch., 1884, p. 32). 



FIG. 19. A cell from nutmeg lying in oil. In the ground mass are very numerous 

 crystals of fat. Some of the granules are compound starch-grannies, but others are 

 protein granules with crystalloids. The rhombic granule has hardly any envelope. 



[Pfeffer.) 



BOQ 



FIG. 20. Globoids of Vitis vinifera. ^. (Pfeffer.1 



FIG. 21. Large protein granules from Vitis vinifera. 5 j. (Pfeffer. ) 



FIG. 22 Wheat-grain, showing cells containing starch-granules. (Schmidt ) 



