2l8 BOTANICAL MICROTECHNIQUE. 



protelds, as may easily be shown by the aid of the reactions 

 described in 224 to 234. When examined in alcohol or 

 glycerine, they are usually hardly or not at all distinguish- 

 able from the fundamental mass, since they have about the 

 same refractive index as it (Fig. 49, II, a). But after being 

 placed in water, in which the crystalloids are always insoluble, 



they show clearly in consequence 

 of their greater density (Fig. 49, 

 II, b). To distinguish them from 

 the globoids and calcium oxalate 

 crystals, one may make use of their 

 ready solubility in very dilute caus- 

 tic potash and their power of be- 

 coming yellow or brown in a solu- 

 tion of iodine and potassium iodide, 

 according to its strength. 



FIG. 49. I. Protein grains of Pee- -r .. ,.-, / T \ * i .. i 



onia.a, from the outer, b, from .Ludtke (I, 77) has lately recom- 



the middle, c, from the inner 11 j 



layers. Drawn from picric acid mended a concentrated aqueous 



II. Protein grains from the endo- Solution of SOdlUm pJlOSpllCtte for 



sperm of Ricinus communis, , . . . ,, . , . 



a. in alcohol, b, on the addition the recognition Ot Crystalloids, SIIICC 



of iodine-potassium-iodide solu- , . ...... 



tion after treatment with alco- they are insoluble in it, while all 



hoi. k, crystalloid; g, globoid. . 



other constituents of the protein 



grain are dissolved by it, though sometimes only after 

 several hours. 



The crystalloids with distinct faces belong, according ta 

 Schimper (I), partly to the isometric and partly to the hex- 

 agonal crystal-system (cf. Figs. 49, II, b and 50, II and III) ; 

 and those of the latter system have a feeble doubly refractive 

 power. 



386. Eosin is very well adapted for staining the fixed 

 crystalloids. Acid fuchsin may also be used for the same 

 purpose according to one of the methods given in 345 

 347. These dyes give a very pure and deep staining of the 

 crystalloids, especially after fixing with corrosive sublimate. 



387. Recently Overton (II, 5) and Poulsen (II) have given 

 methods for staining crystalloids. Overton places sections 

 of the endosperm of Ricinus, hardened with alcohol, first ia 



