CHLOROPHYLL. 



[ 138 ] 



CHLOROPHYLL. 



without large granulations in the general 

 mass, but with a number of distinct, large, 

 bright-looking corpuscles at intervals (PI. 5. 

 fig. 18). In Protococcus, in zoospores, and 

 in the indi\Tidual ciliated bodies of the Volvo- 

 cineae, the chlorophyll appears to tinge the 

 general mass of granular protoplasm, leaving 

 the conical apex (beak) uncoloured (Plates 

 3 & 5), while more or less distinct corpuscles 

 or granules are scattered through the mass, 

 varying in number and size at different 

 periods. When any of these forms of chloro- 

 phyll are treated with aether or alcohol, the 

 colour is abstracted, while the organized forms, 

 the corpuscles, &c., remain, so that the true 

 chlorophyll is really only a soluble substance, 

 dyeing thebodies called chlorophyll-granules, 

 &c. It becomes a question then whether 

 these are homogeneous, semi-solid corpus- 

 cles, or vesicles containing the colouring 

 matter in sacs, from which it is extracted by 

 the aether, &c. Nageli and others assert the 

 vesicular character of the chlorophyll-cor- 

 puscles, and the appearances are sometimes 

 much in favour of this view, but in the many 

 cases in which we have obtained the appear- 

 ance of a double hne around them, under 

 high magnifying powers, we have never been 

 able to divest ourselves of tlie impression 

 that this was an optical deception. Nageli 

 asserts that the corpuscles multiply by divi- 

 sion, which is probable, but does not prove 

 that they are vesicular structures. The 

 observation of Goppert and Cohn, of a chlo- 

 rophyll-corpuscle swelling up and bursting 

 through endosmose, may be explained with- 

 out supposing a regularly organized coat. 

 We are inclined to believe that the bodies 

 bearing the green colouring matter are struc- 

 tures belonging to the protoplasm, the green 

 colour being only an additional character, 

 produced by the action of light, superadded 

 to the ordinary character of the granular 

 structures occurring in the protoplasm or 

 nitrogenous cell-contents. See Protoplasm. 

 A very important point connected with 

 chlorophyll is its relation to starch. Thebodies 

 called starch-granules occur verj' commonly 

 with chlorophyll-corpuscles in the cells of 

 green parts of plants, and they become sub- 

 stituted for each other under varying circum- 

 stances. Some authors have imagined that 

 chlorophyll is produced by a chemical 

 decomposition of starch, while others think 

 that starch is developed from chlorophyll. 

 The chief ground for the latter view is the 

 fact, that starch-granules, one, or a group of 

 many, are often fovmd in the centre of chlo- 



rophyll-corpuscles, like a kind of nucleus. We 

 have traced, in Hepaticaceae, the gradual 

 formation of a group of starch-granules in 

 the interior of a chlorojihyll-corpuscle (where 

 they are readily detected by the application 

 of iodine), and this goes on in certain cases 

 until almost all the green colour is lost. 

 Starch occurs universally at a certain period 

 in the bright distinct chlorophyll-corpuscles 

 of Chara and of the Confervaceae, Sjjirogyra, 

 &c., so that these are coloured blue by 

 iodine, although green before its application. 

 But this starch may disappear again in the 

 course of nature, for it always vanishes from 

 these corpuscles when they are about to 

 become organized into zoospores. In fact 

 the green chlorophyll is predominant during 

 active vegetation, and starch in periods of 

 rest or in full-grown structures. Moreover, 

 while chlorophyll may aj^pear independently 

 in young cells, without being preceded by 

 starch, in green tissues, starch makes its 

 appearance without previous existence of 

 chlorophyll-corpuscles in subterraneous struc- 

 tures, as for example in the potato and other 

 tubers. The truth of the matter therefore 

 appears to be, that the chlorophyll struc- 

 tures, as above stated, are granular structures 

 belonging to the general protoplasm or nitro- 

 genous cell-contents ; that they become 

 coloured green in the light by a chemical 

 change connected with the vital processes ; 

 that in undergoing this change they do not 

 lose the power, which the ordinary protoplasm 

 ])0ssesses, of secreting starch, and decompo- 

 sing it again when required for the nutrition 

 of the plant. Starch-granules, when free 

 and uncoloured, appear to be produced ori- 

 ginally from granular or vesicular proto- 

 plasmic structures, only differing by absence 

 of colour from chlorophyll structm'cs. For 

 example, the granular protoplasm around 

 the cell-nucleus in the cells of herbaceous 

 Monocotyledons (such as the Lily, Trades- 

 cantia, &c.) will sometimes become converted 

 into chlorophyll-granules (in superficial cells), 

 inside which starch may be subsequently 

 developed ; but (in deeper-seated cells) the 

 granular protoplasm may give rise at once 

 to starch-granules (PI. 36. fig. 28 «) without 

 the previous existence of the green modifi- 

 cation of the protoplasm, i. e. chlorophyll. 



Chlorophyll is turned yellow-brown by 

 tincture of iodine ; sulphuric acid gives it a 

 more or less deep blue colour; aether and 

 alcohol (hscharge the green tint. Prepara- 

 tions put up in chloride of calcium lose their 

 green colour ; those preserved in water will 



