J92 



Vegetable Plnjsiolof/y. 



to this, very superficial and incorrect notions prevail widely as 

 to the physical and chemical qualities of chlorophyll, and its 

 developmental relations to the other substances occurring in cells. 

 Chlorophyll is ordinarily found in the form of rounded ijra- 

 nules, flattened in one direction, lying imbedded in the la^er of 

 colourless protoplasm lining the cell-wall. In this condition it 

 may be readily observed in the internal cells of the leaves of the 

 grasses (fig. 9, a), and even more clearly in the cells of the leaves 

 of the water-plant Vallisneria. The depth of the colour and the 

 number of granules vary according to circumstances, both being 

 increased by active solar influence. When the granules are so 

 numerous that they are crowded together, they often assume a 

 hexagonal form, so as to fit closer together, but even when thus 

 crowded, they are not immediately in contact, a thin layer of the 

 colourless protoplasm being always interposed between tliem. 



When fully developed, chloro- 

 Fig. 10. pliyll is ordinarily granular, and 



A situated as described upon the wal\ 



of the cell, but there are exceptions 

 to this rule, especially among the 

 flowerless plants, where the chloro- 

 phyll sometimes occupies the centre 

 of the cell, surrounding the nucleus, 

 and sending out radiating processes 

 ( Aidhoceros), while in otlier cases 

 it presents itself in the form of 

 bands and streaks running over the 

 cell-wall, quite distinct from the 

 layer of protoplasm immediately ap- 

 plied to this (^Spirogyra, fig. 10). In 

 many cases also, where the chloro- 

 phyll is ultimately found in the 

 form of distinct large granules, it 

 appears at first like a mass of soft 

 granular protoplasm, of a light 

 ^^/5^ I green tint, from which the granular 



\ "1 bodies are gradually formed. Thus 



in the cells just beneath the corky 



afilamcntof ypiro(7'/?-a, with i . r . ^ , ^ ■ . t...i 



the green colouring matter in the form of SKin Ol potatoCS (COUtamiUg little 



broad bands (a;, ^spirally arranged ; in starch"^ whichhave become 



the bands lie groups of minute starch- "^ ^"' biaicu^, niiicu xidvc; uecuiiic 



by exposure to light, the 

 colour is found first in the 



green 

 green 



granules (b), which appear as bright 



points, but are coloured blue by iodine. 



B. A cell laid in syrup, in which exosmotic 



action has c;iusud the colourless prinior- ,1 i c ' ' 1 *.!„ 1, ;„U 



dial utricle to contract, carrying the threads ot VlSCld protoplasm whlCll 

 green bands with it, leaving the cell- walls gtretch OUt frOm the UUclcUS aCrOSS 

 iree. ilagnihed '^00 diameters. 11 r 1 1 r 



the cell. In young cells ot the leal 

 of a moss {Hyprmm) the chlorophyll appears at first as a green 



