SECT. I 



MORPHOLOGY 



63 



green colour, the chloroplasts eitlier do not develop, or they are 

 colourless, or have only a brownish or reddish colour. No chroniato- 

 phores are found in the Fungi. 



Leueoplasts. — In the interior of plants, where light cannot 

 penetrate, leueoplasts are developed from the rudiments of the 

 chromatophores instead of chloroplasts. They are of a denser con- 

 sistency than the chloroplasts, mostly spherical in shape, but often 

 somewhat elongated in consequence of enclosed albuminous crystals. 

 If the leueoplasts become at any time expased to the light, they may 

 change into chloroplasts. This frequently occurs, for example, in 

 the superficial portions of potato tubers. 



Chromoplasts. — The chromoplasts of most flowers and fruits arise 

 either directly from the ludiments of colourless chromatophores, or 





Fio. 03. — CeU from the upper surface of the 

 calyx of Trojiaeolum majus, showing 

 chromoplasts. (x 540.) 



^ 



Fio. 64. — Chromoplasts of the Carrot, some 

 with included starch grains, (x 540.) 



from previously formed chloroplasts. In shape the chromoplasts 

 resemble the chloroplasts, except that they are usually smaller ; in 

 consequence of the crystallisation of their colouring pigment they 

 sometimes assume triangular, tabular, needle, or fan-shaped shapes 

 (Figs. 63, 64). The colour of the chromoplasts varies from yellow 

 to red, according to the predominance of yellow xanthophyll or 

 orange-red carotin. The name carotin (■**^) has been derived from 

 the Carrot (Daucus Carota), in the roots of which it is particularly 

 abundant. (Fig. 64). The frequent crystalline form of the chromo- 

 plasts is, in a great part, due to the tendency of carotin to crystallisa- 

 tion, although it may be also occasioned by needle-like crystals of 

 albumin. Xanthophyll, however, is never present in the chromoplasts 

 except in an amorphous condition. 



Inclusions of the Protoplasts. — The main inclusions of the 

 protoplasts met with are starch, aleurone, organic and 



inorganic 



