46 MORPHOLOGY OF THE CELL. 



are never in immediate contact with the cell-sap, but are enveloped on all sides by the 

 colourless protoplasm. Their chemical and physical properties distinctly show that 

 their colourless ground-work is a substance altogether similar to protoplasm. The 

 chlorophyll-bodies consequently always behave as integral parts of the protoplasm ; 

 and this is especially evident in the division of cells containing chlorophyll, in 

 conjugation, in the formation of swarm-spores, &c. But the chlorophyll-bodies, 

 when once formed, grow, and if they possess roundish forms they may be increased 

 by division. Both appear always to depend on the growth of the collective proto- 

 plasm-body in which they are deposited. 



It is only in the Algae that the forms of the chlorophyll-bodies show much 

 variety ; in them it is frequently the case that the whole protoplasmic body, with 

 the exception of an outermost layer, or of a little more than this, either appears 

 homogeneously green [e.g. many swarm-spores, Palmellacese, gonidia of Lichens) or 



the chlorophyll-grains assume stellate forms 

 {e. g. Zygnema criiciatum, Fig. 45), or they 

 form several lamellae which have the appear- 

 ance of a star when the cell is cut across (as 

 in Closterium, &c.), or straight or spiral bands 

 ~ ~ ~ {e. g. Spirogyra). But in most Algce and all 



VlG. 45-— ■'^ceW of Zyo-nei^ta criic/'ahim, withtwosteUnte jtt 



chlorophyll-bodies which are suspended in the interior of MOSSCS aUQ VaSCUlar plaUtS, tllC ChlOrOpliyll- 



the cell; they are united bj' a colourless bridge of proto- . 



plasm in whicli lies a nucleus ; the rays which form the bodlCS are TOUUdcd Or pOlygOUal maSSCS 



union with the parietal sac are already nearly colourless in 



the middle. In ea.h of the two chlorophyll-bodies lies a collcctcd arounQ Q, ccntrc, aud arc tcmied 



Grains of Chlorophyll. Generally a large 

 number are contained in one cell, sometimes, however, only a few relatively large 

 ones {e.g. Selaginella), and in one of the Hepatic^e of simplest structure (An- 

 thoceros) only a single grain of chlorophyll is to be found, enclosing the 

 nucleus ; this therefore, when the cells divide, itself also divides in a correspond- 

 ing manner. 



With extremely few exceptions Grains of Starch arise in the homogeneous 

 solid substance of the chlorophyll-bodies, and, where these have special forms, are 

 distributed in definite places (cf. e. g. Fig. 5) ; in the ordinary chlorophyll-grains 

 they arise in the interior in larger or smaller numbers. They are at first visible 

 as points, gradually increase in size, and finally may so completely fill up the space 

 of the chlorophyll-grain that the green substance is represented only by a fine 

 coating on the mature starch-grain ; even this coating may, under certain circum- 

 stances, disappear (as in old yellow leaves of Pisiun sativum, Nicotiana), and the 

 starch-contents then lie in the cell (destitute of protoplasm) in the place of the 

 chlorophyll-grains. Sometimes drops of oil also form in the interior of the chloro- 

 phyll-substance {e. g. in the bands of Spirogyra) ; and here and there granular 

 contents of an unknown nature are observed. All these structures which arise in the 

 chlorophyll-bodies are, however, not constant portions of them ; their appearance 

 and disappearance depend entirely on the light, temperature, and on other circum- 

 stances ; the appearance of the chlorophyll-bodies themselves is also bound up with 

 these conditions of life, to a description of which we shall not recur till Book III, 

 where it will be shown that chlorophyll is one of the most important elementary 

 structures, and that its contents are especially its products of assimilation. The 



