52 IV. PLASTIDS. 



a moss is Mnium hornum, or Funaria hygrometrica. Numerous 

 chlorophyll bodies of considerable size are to be seen in every 

 cell ; l in plants which are exposed to diffused daylight they are 

 contiguous only to the free cell-walls ; that is, to those which 

 form the upper and under surface of the leaf. 2 Hence they 

 present their broadside to the observer. That they are narrower 

 in profile we see in the isolated grains which underlie the side 

 walls. All stages of division of the chlorophyll bodies are easy 

 to find, and often associated in the same cell (Fig. 17). The 

 resting grains appear quite circular ; they then 

 become elliptic, afterwards constricted in the 

 middle so as to be shaped like a figure of eight, 

 and finally completely divided across. The twin 

 grains remain for some time still in contact. The 

 starch enclosures of the chlorophyll bodies are, 

 on account of their varying size, in many leaves 

 easy, in others difficult, to see. They are, however, 



hygrometrica, rest- alwavs clearlv distinguishable when the chlorophyll 

 ing and in division. . ,. J J 



bodies get out of an opened cell into the surround- 

 ing water, and are there disorganised. With this object we cut a 

 leaf with a sharp pair of scissors into several pieces. The starch 

 grains, set free from the disorganised chlorophyll bodies, augment 

 in size, and are identified as such with iodine. On the other hand 

 an entire uninjured chlorophyll body is coloured murky brown 

 with iodine, from a combination of the blue coloration of the 

 starch enclosures, the yellowish-brown coloration of the proto- 

 plasmic ground substance, and the green of the chlorophyll. In 

 order to obtain favourable iodine coloration of the uninjured 

 chlorophyll bodies, we take for study leaves which have lain some 

 time in alcohol, and are thereby decolorised. The chlorophyll 

 bodies now appear colourless ; their starch enclosures become 

 coloured, by gradual action of the iodine solution, more quickly 

 than the protoplasmic body. The iodine reaction is still more 



lr The cell- walls and cytoplasm of this leaf are sufficiently resistant to 

 permit the preparation to be put up in water without the chromatophores 

 suffering. In many cases, however, they are injured by water, and it has been 

 recommended then to put the preparation in pretty fresh olive oil, in which 

 the cells not merely remain alive for a long time, but the oil serves to expel 

 the air from the intercellular spaces, and, from its refractive properties, 

 increases the transparency of the preparation. A dilute solution of a neutral 

 salt, or of sugar, as advised for living cells, may also be used. [ED.] 



2 This is known as the position of Epistrophe. 



