CHLOROPHYLL. 



[ 168 ] 



CHLOROPHYLL. 



CHLOR'OPHYLL (leaf-green). — The 

 name applied to the green colouring-matter 

 of plants. The nature of tlie substances which 

 are understood under this term is still some- 

 what questionable. It is ordinarily stated 

 that chlorophyll exists commonly under the 

 form of globules or granules, and occasion- 

 ally as an amorphous granular substance, 

 in either case more or less adlierent to, or 

 imbedded in the primordial utricle of the 

 cell. It is, lioweyer, a contested point 

 whether the chlorophyll-corpuscles are se- 

 misolid homogeneous globules in which the 

 chlorophyll is imbedded, or vesicles com- 

 posed of a delicate membrane enclosing a 

 green liquid : the former view is now, how- 

 ever, g'enerally adopted. Chlorophyll pre- 

 sents itself in the form of distinct corpus- 

 cles (f/ranuku of authors), in the cells of 

 the flowering plants generally, particularly 

 the parenchyma of leaves and the subepi- 

 dermal parenchyma of green stems and 

 shoots. The granules are especially large 

 and distinct in certain water-plants, and 

 may be well seen lying scattered, singly, 

 imbedded in the circulating protoplasm of 

 the cells of the leaves of Vallianeria and 

 other water-plants. The corpuscles are very 

 evident in the cells of the prothallia of 

 Ferns, in the leaves of SelcKjineUa, of Mosses 

 and Liverworts ; also in Chcira, where they 

 are very abundant and form a continuous 

 layer, or numerous rows, embedded in a 

 gelatinous stratum between the cell-w^all 

 and the circulating mass of protoplasm. In 

 the Oonfervoids the chlorophyll often ap- 

 pears both formless and corpuscular in one 

 and the same cell, but usually more or less 

 formless in young cells, and more com- 

 pletely converted into granules in the full- 

 grown, as in Vaucherin. In the Confer- 

 vacoa3, such as Cladophorn., and in CEdogo- 

 niuni, it presents itself in a granular stratum 

 with numerous larger bright corpuscles ; 

 and in Hpinxiyra, Zi/tjnema, &c. the chlo- 

 rojiliyll takes the form of tlie spiral or an- 

 nular band to which it is adherent, without 

 large granulations in the general mass, but 

 with a number of distinct, larg(;, bright- 

 looking corpuscles at intervals (I'l. Si. fig. 

 18). In Profococcus, in zoospores, and in 

 the indiyidual ciliated bodies of the Vol- 

 vocineai, the chloropliyll appears to tinge 

 the general mass of granular protoplasm, 

 leaving the conical apex (beak) uncoloured 

 (I'lates 7 & 9), while more or less distinct 

 corpuscles or granules are scattered through 

 tie mass, varyiu"' in number and size at 



different periods. When any of these forms 

 of chlorophyll are treated with ether, benzole, 

 alcohol, or chloroform, the colour is abstract- 

 ed, while the organized forms, the corpuscles, 

 &c., remain ; so that the true chlorophyll is 

 really only a soluble substance, dyeing the 

 bodies called chlorophyll-corpuscles &c. 

 It becomes a question then whether these 

 are homogeneous semisolid corpuscles, or 

 vesicles containing the colouring-matter in 

 sacs,' from whicli it is extracted by the ether 

 &c. Nageli and others assert the vesicular 

 chai'acter of the chlorophyll-corpuscles and 

 the appearances are sometimes much in 

 favour of this view ; but in the many cases 

 in which Ave have obtained the appearance 

 of a double line around them, under high 

 magnifying powers, we have never been 

 able to divest ourselves of the impression 

 that this was an optical illusion. Nageli 

 asserts that the corpuscles multiply by di- 

 vision, which is true, but does not prove 

 that they are vesicular structures. The ob- 

 servation of Giippert 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 tlie bodies 

 bearing the green colouring-matter are 

 structures belonging to the protoplasm, the 

 green colour being only an additional clia- 

 racter, produced by the action of light, 

 superadded to the ordinary character of the 

 granular structurs occurring in the proto- 

 plasm or nitrogenous cell-contents. See 

 Protoplasm. 



A very important point connected with 

 chlorophyll is its relation to starch. The 

 bodies called starch-granules occur very 

 commonly with clilorophyll-corpuscles in 

 the cells of the green parts of plants, and 

 they become substituted for each other 

 under varying circumstances. Some authors 

 have imagined that chlorophyll is produced 

 by a chemical decomposition of starch, 

 while others think tliat starch is deyeloped 

 from chlorophyll. The chief ground for 

 the latter view is the fact that starch- 

 granules are often found in the centre of 

 chlorophyll-corpuscles, like a kind of nu- 

 cleus. "We have traced, in Hepaticie, the 

 gradual formation of a group of starch- 

 granules in the interior of a chlonjpliyll- 

 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 

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