MORPHOLOGY 



59 



!i'\'6_S. 



■■UMtM 

 M:\ oh 



mm 



foliage its autumnal brilliancy. In the leaves of coniferous trees, 

 which only indicate the approaching winter by assuming a somewhat 

 brownish tint, the case is different. The 

 chlorophyll-green of their chloroplasts changes 

 to a brownish green, but in the following 

 spring regains its characteristic colour. 



In such phanerogamic parasites or humus- 

 plants as are devoid of green colour, the 

 chloroplasts either do not develop, or they 

 are white, or have only a brownish or green- 

 ish colour. No cbromatophores are found 

 in the Fungi. 



In the interior of plants, where light 

 cannot penetrate, LEUCOPLASTS are developed 

 instead of chloroplasts from ,the rudiments 

 of the chromatophores. They are of a denser 

 consistency than the chloroplasts, and re- 

 sembling a flattened ellipsoid in shape, are 

 often somewhat elongated in consequence of 

 enclosed albuminous crystals. If the leuco- 

 plasts become at any time exposed to the 

 light, they not infrequently change into 

 chloroplasts. This frequently occurs, for ex- 

 ample, in potatoes. 



The GHROMOPLASTS of most flowers and 

 fruits arise either directly from the rudiments 

 of colourless chromatophores, or from pre- 

 viously formed chloroplasts. In shape the 

 chromoplasts resemble the ellipsoidal granules 

 of the chloroplasts, except that they are 

 usually smaller ; or, in consequence of the 

 crystallisation of their colouring pigment, they FlG 60 

 assume a triangular, tabular, needle, or fan- 

 shaped form (Figs. 57, 58, 59). The colour of 

 the chromoplasts varies from yellow to red, 

 according to the predominance of xanthophyll 

 or carotin. 



The name carotin has been derived from the Carrot (Daucus 

 Carota), in the roots of which it is particularly abundant (Fig. 59). 

 The frequent crystalline form of the chromoplasts is, in a great part, 

 due to the tendency of carotin to crystallisation, although it may be 

 also occasioned by needle-like crystals of albumen. Xanthophj'll, 

 however, is never present in the chromoplasts except in an amorphous 

 condition. 



Multinuelear Cells. — While the cells of the Cormophytes are 

 almost exclusively uninuclear, in the Thallophytes, on the contrary, 



A cell of CIriflopli.ora 

 glomeratcr, fixed with 1 per cent 

 chromic acid and stained with 

 carmine, n, Nuclei ; ch, chro- 

 matophores ; /', pyrenoids ; ■<, 

 starch grains. ( x 540. ) 



