48 MORPHOLOGY OF THE CELL. 



antheridia of Mosses and Characeae become, at the time of fertilisation, of a 

 beautiful red; in ripening fruits {Lycium barbarum, Solanuin pseudo-capsicum, Sec), 

 the change of colour from green to yellow and red depends also on a similar loss 

 of colour of the chlorophyll-granules, accompanied by a breaking up into angular 

 forms with two or three points (Kraus, /. c). Nearly related to the chlorophyll- 

 granules are the vehicles of the yellow colouring materials to which many petals 

 owe their colour {e.g. Cucurbita). The occasional blue {Tillandsia anicena) or brown 

 and violet bodies {Orchis Morio) are much further removed from this type, although 

 they also have a basis similar to protoplasm, which is tinged by a colouring material, 

 in these cases soluble in water. . 



(a) The Substance of the Chlorophyll-bodies is, irrespectively of the contents referred 

 to, destitute of those fine granules which are so generally distributed through colourless 

 motile protoplasm. In spite of their sharply defined form they are very soft and 

 greasy when crushed; when they come into contact with pure water, vacuoles are 

 formed, which at last burst through the green substance as hyaline bladders. Young 

 chlorophyll-granules may thus become converted into delicate bladders, in which the 

 starch-grains remain ; old grains have much greater consistence. After extraction of 

 the green colouring matter out of true chlorophyll-bodies, e. g. the bands of 

 Spirogyra or granules of Allium Cepa, the remaining colourless basis possesses greater 

 power of resistance, is coagulated, and shows all the reactions of protoplasm already 

 mentioned. 



(b) The Origin of the Chlorophyll-bodies has at present only been directly observed 

 in the granular forms; it can to some extent be compared with the process of free 

 cell-formation. Round centres of formation within the protoplasm small portions of 

 it collect in defined masses; if the centres of formation are at a considerable dis- 

 tance from one another, the chlorophyll-granules become round (as in the hairs 

 of Cucurbita)', but if they are large and lie close to one another, they are at 

 first polygonal, as if flattened by pressure. The process then resembles the formation 

 of numerous small swarm-cells in a single cell of Achlya (Fig. 9, A, p. 13); only that 

 in this latter case colourless protoplasm always continues to lie between the green 

 portion, as in the parietal chlorophyll of the leaves of Phanerogams. If a mass of 

 protoplasm collects round the central nucleus during the formation of chlorophyll, 

 the granules are often formed in its neighbourhood ; they may then revolve with the 

 protoplasm in the cell, or afterwards assume definite positions. In the filamentous 

 Algae with apical growth {e.g. Faucheria, Bryopsis), they are produced in the colourless 

 protoplasm-mass of the growing end of the filament, and then remain closely 

 applied to the wall. In ripe spores of Osmunda regalis the chlorophyll surrounds the 

 nucleus in the form of amorphous cloudy masses, which, however, separate on germi- 

 nation as ovoid granules, at first weakly defined, afterwards more sharply (Kny). In 

 those cells of young leaves of Phanerogams which contain chlorophyll (cotyledons 

 of the sunflower, primordial leaves of Phaseolus, buds of the tubers of the Jerusalem 

 artichoke, &c.) a definite layer of hyaline protoplasm devoid of granules is to be observed, 

 close to the cell-wall, in which the chlorophyll-granules are subsequently formed ; here the 

 appearance is sometimes presented as if the mass were cut up into polyhedral pieces. 

 The formation of the chlorophyll-granules is not always contemporaneous with that 

 of its colouring matter ; they may be at first colourless (as in Faucheria or Bryopsis, 

 according to Hofmeister) or yellow (in the case of leaves of Monocotyledons or 

 Dicotyledons imperfectly exposed to light or in process of development), and be- 

 come green at a subsequent period; in the cotyledons of Coniferae the green colour 

 appears contemporaneously with their origin even in the dark when the temperature 

 is sufficiently high, as also in Ferns. The chlorophyll-granules, after assuming their 

 green colour, grow by intussusception to many times their original size; if they are 



