SPECIAL METHODS. 2OI 



results (cf. 323) are poorly suited to plant-cells, according 

 to Guignard (IV, 167). I have obtained, also, in some not 

 very extended experiments with Hermann's methods, no 

 staining of the centrospheres, while the spindle-threads of 

 such preparations stood out very sharply, especially after 

 staining with gentian violet. 



3. The Chromatophores and their Inclusions. 



349. Under the name chromatophores are commonly in- 

 cluded at present three different kinds of bodies ; the green 

 chlorophyll-bodies, chloroplasts, and the corresponding bod- 

 ies in the algae which are not green, the mostly yellow or 

 red bodies which carry coloring matters, chromoplasts, oc- 

 curring especially in the bright-colored parts of flowers and 

 fruits, and the colorless leucoplasts, which are found chiefly 

 in subterranean and young parts of plants. The grouping 

 of these different bodies together is justified, aside from 

 their chemical similarity, by the fact, recognized especially 

 by Schimper, that they stand in genetic relations with each 

 other, and may pass over into each other in the most vari- 

 ous ways 



I. Methods of Investigation. 



350. The study of chromatophores has been conducted 

 chiefly in the living cell. Of course this is only possible in 

 sections which are at least several cell-layers in thickness; 

 and the most rapid preparation possible is necessary, since 

 chromatophores are very sensitive to the most varied harm- 

 ful influences. Since most cells also die very quickly in 

 pure water, and the chromatophores especially suffer .pro- 

 found structural changes in this medium, it is advantageous 

 to use a dilute solution of salt or sugar as a medium for 

 their study. I have used with good results a $% solution of 

 sugar, with which I injected the tissues to remove the air 

 from the intercellular spaces, which may usually be easily 

 done by means of a filter pump (cf. also 5). 



351. In difficult cases one must have recourse to staining 

 methods. I have found a concentrated alcoholic solution of 



