CHLOROPHYLL. 



[ 169 ] 



CHLOROPHYLL. 



chlorophyll-corpuscles of Chara and of 

 the Oonfervaceee, Spirogyra &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 chloro- 

 phyll is predominant during active vegeta- 

 tion, and starch in periods of rest or in full- 

 grown structures. Moreover, while chloro- 

 phyll may appear independently in young 

 cells without being preceded by starch, in 

 green tissues starch makes its appearance 

 without previous existence of chlorophyll- 

 corpuscles in subterranean structures, as for 

 example in the potato and other tubers. 

 The truth of the matter therefore appears to 

 be, that the chlorophyll-structures, as above 

 stated, are granular structures belonging to 

 the general protoplasm or nitrogenous cell- 

 contents, that they become coloured green 

 in the light by a chemical change connected 

 with the vital processes, and that in under- 

 going this change they do not lose the power, 

 which the ordinary protoplasm possesses, of 

 secreting starch and decomposing it again 

 when required for the nutrition of the plant. 

 Starch-granules, when free and uncoloured, 

 appear to be produced originally from gra- 

 nular or vesicular protoplasmic structures, 

 only differing by absence of colour from 

 chlorophyll structures. For example, the 

 granular protoplasm around the cell-nucleus 

 in the cells of herbaceous Monocotyledons 

 (such as the Lily, Tradescantia c.) will 

 sometimes become converted into chloro- 

 phyll- granules (in superficial cells), inside 

 which starch may be subsequently deve- 

 loped ; but (in deeper-seated cells) the 

 granular protoplasm may give rise at once 

 to starch-granules (PL 46. fig. 28 a) with- 

 out the previous existence of the green 

 modification of the protoplasm, i. e. chloro- 

 phyll. 



The views of the nature of chlorophyll 

 above expressed (in the first edition of this 

 work) have been since confirmed by the 

 observations of v. Mohl and Gris ; and re- 

 peated observations have furnished us with 

 similar results. In Caspary's observations 

 on Hydrillese also, will be found confirma- 

 tion of the statement that the supposed 

 vesicular structure is an illusion. 



Chlorophyll occurs in the animal, as well 

 as in the vegetable kingdom thus in Infu- 

 soria (Stentor &c.), the zoophytes (Hydra), 

 the Turbellaria, Aphidae, &c. 



Chlorophyll-corpuscles, when set free in 

 water, expand by imbibing water, some- 

 times becoming vacuolated and bursting. 

 Alcohol and most acids coagulate them, 

 while acetic acid will often blend the cor- 

 puscles into an irregular mass. 



After the separation of the chlorophyll, 

 the protoplasmic base retains both its form 

 and volume j constituting a solid soft body, 

 often containing small vacuoles. 



Chlorophyll is turned yellow-brown by 

 tincture of iodine ; sulphuric acid gives it a 

 more or less deep blue colour ; ether and 

 alcohol discharge the green tint. Prepara- 

 tions mounted in chloride of calcium or 

 glycerine often lose their green colour ; those 

 preserved in water wih 1 sometimes retain it 

 a long time. The green colouring-matter 

 extracted by alcohol is a complex substance, 

 containing a kind of wax and a matter 

 allied to indigo. 



It was formerly considered that chloro- 

 phyll was the only colouring-matter of 

 plants, capable under the influence of oxy- 

 gen of producing all the varied and beauti- 

 ful colours of flowers. Subsequently, two 

 colouring-matters, a blue-phyllocyanine, and 

 a yellow-phylloxanthine, have been sepa- 

 rated by chemical reagents, and considered 

 as the real colouring-matters, which by 

 their mixture produced the most varied 

 colours. The old view has lately been re- 

 vived ; but the whole question must at 

 present be considered as unsettled. 



In autumn, at the fall of the leaf, the 

 chlorophyll becomes dissolved, and con- 

 veyed to the perennial portions of the plants, 

 the cells become filled with liquid contain- 

 ing crystals and a number of bright yellow 

 granules ; if the leaves are red, this arises 

 from a substance dissolved in the liquid, the 

 yellow granules being also present. 



BIBL. Mohl, Veget. Cell. (Trawl. 1852), 

 41 ; Vermischte Schriften, 349 ; JBotan. Zeit. 

 1855 (Ann. N. H. 2nd ser. xv. 321); 

 Nageli, Zeitsch. f. wiss. Bot. iii. 110 (Ray 

 Soc. 1849); Mulder, Physiol. Chem., Tr. 

 266 ; Goppertand Cohn, Bot. Zeitung, 1849, 

 vii. 665; Schleiden, Grundziige wiss. Bot. 

 3rd ed. 196 ; Braun, Verjung. (Ray Soc. 

 1853, 195); Morot, Color. desVegetaux,Ann. 

 Sc. Nat. 3 ser. xiii. 160 ; GuiUemin, Ann. 

 Sc. Nat. 4 ser. vii. 155; Gris, ibid. 1857, 

 vii. 179; Caspary, Pi'ingsheims Jahrb. wiss. 

 Bot. i. 399, ibid. 1881; Fremy, Compt. 

 Rend., 1. 405 ; Gmelin, Handb. Chem. vii. 

 1430 ; Hofmeister, Pflanzenzelle, 1867, sect. 

 41 ; Kraus, Jahr. wissensch. Bot. 1871, viii. 



