204 BOTANICAL MICROTECHNIQUE. 



rhombic plates or peculiar cylindrically curved bodies, as, 

 for example, in the parenchyma of the carrot (cf. Fig. 39, 

 II); or it occurs in the form of delicate needles which are 

 imbedded in the colorless stroma in small numbers, as in 

 Neottia nidus-avis (Fig. 39, I), or in large quantity, as in the 

 pericarp of Sorbus aucuparia (Fig. 39, III). All these pig- 

 ment-crystals, which consist of carotin, according to the 

 prevailing nomenclature, are characterized by strong pleo- 

 chroism *), and this peculiarity has been used by Schimper 

 (III, 94) in difficult cases for the recognition of the crystal- 

 line structure of the fine pigment-needles. 



357- The amorphous pigment occurs within strongly re- 

 fractive globules (** grana ") which are imbedded in the 

 usually quite colorless stroma. The flesh- 

 colored fertile stems of Equisetum arvense con- 

 tain chromatophores with especially large 

 grana (Fig. 40). 



The study of the crystalline and amorphous 

 pigments can, of course, be carried on with 



FIG. 40. Chromo- r 



^rSici/ni? l of ent ^ re certainty only within the living cells, 

 *f em ar5'~ an d> on account of their ready decomposition, 

 (Xi4oo.) t h e precautions described in 350 should be 



very strictly adhered to. 



III. The Inclusions of the Chromatophores. 



358. The most widely distributed of the inclusions of the 

 chromatophores, the starch-grains, will be treated in connec- 

 tion with various related bodies in 400 and following ones. 

 Besides these, there have been recognized in the chromato- 

 phores protein crystalloids, leucosomes, pyrenoids, and oil- 

 drops, which will now be discussed in order. 



* This is determined by observing the body with one nicol prism, prefer- 

 ably the polarizer, and turning either the nicol or the crystal. Pleochrolc 

 objects then appear quite colorless in one position, or at least very light 

 colored, and, after rotation through 90, more deeply colored than without 

 the use of the nicol. 



