CHLOROPHYLL. 103 
the chlorophyll granules are seldom found unchanged, mostly 
forming within the cells shapeless masses, in which the granular 
structure can be recognized only with difficulty. 
A similar condition also exists with regard to the maintenance 
of the coloring matter, the chlorophyll.’ If, namely, leaves are 
quickly dried, the plant. acids act but slightly upon the chloro- 
phyll, only a little brownish-yellow chlorophyllan- (an oxi- 
dation product of chlorophyll) is formed, and the leaves remain 
handsomely green. If, however, they are dried without care 
and slowly, brownish-yellow leaves are obtained, in consequence 
of the abundant formation of chlorophyllan.* Some leaves, how- 
ever, become brown even with the most careful drying (Vico- 
tiana, Juglans). 
Since the formation of chlorophyll is dependent upon light, 
_ it is found only in those parts of plants which grow above ground 
and are exposed to the light.* Leaves developed in the dark are 
yellow (<‘ etiolement” etiolation ; the coloring matter is called 
etiolin’). All leaves and green shrubs contain chlorophyll, 
although it is sometimes conceaied by red coloring matters dis- 
solved in the cell-sap (Dracena leaves). We meet with it also 
in seed-vessels (Juglans), and in barks, especially in the thinner 
ones (Rhamnus, Salix, etc.). Since, however, it occurs only in 
cells which still possess the functions of life, it is wanting in 
such barks as consist entirely of permanent tissue, or in which 
the peripheral layer is wanting (Cinchona, Cinnamon). 
The chlorophyll coloring matter, being a harmless green color, 
is of practical importance. 
'The name enssisiy aber must remain confined to the coloring sub- 
stance. 
* These circumstances have been thoroughly considered by Tschirch: 
**Einige practische Ergebnisse meiner Untersuchungen tiber das Chloro- 
phyll,” in Arch, der Pharm., 1884. 
3 Nevertheless, the half-underground leaf-bases of Rhizoma /filicis are 
also green. Exceptions are presented also by many green embryos en- 
closed by untransparent fruit-casings, and by the small embryos of the — 
Coniferze, developed in the dark. 
‘From the French word étioler, to eticlate or become blanched, 
which is derived from the latin stipula, halm. 
