78 pringsheim's researches on chlorophyll. 



stance differentiated to form a hollow body, the circum- 

 ference of which is abundantly and uniformly pierced in a 

 sieve-like manner, It has, in fact, the character of a hollow 

 sponge. It is difficult to accomplish complete decolorisation 

 by heating in warm water alone, and this is best and most 

 easily brought about by a combination of warmth and dilute 

 acids. The character of the tissue must be taken into 

 account, as, for different tissues one or other method may 

 be more favourable. This character of the ground-substance 

 becomes evident if the corpuscle be decolorised by alcohol or 

 other solvent, and also, as will be presently described, by the 

 action of intense light (fig. 26) ; and the fact that the opera- 

 tion of these different agencies demonstrates the same struc- 

 tural characters in the decolorised chlorophyll-corpuscles is 

 strong evidence that this is also the structure of the corpuscle 

 under normal conditions. Chloro})hyll-bands, plates, and 

 masses show equally well this structure. 



These, the normal effects of heating a tissue in water or 

 exposing it to steam, may be complicated by the temperature 

 being so high as to affect the starch contained in the 

 chlorophyll-corpuscles, and by causing the granules to swell 

 and rupture the corpuscle thus destroy its form. All tissues 

 are not equally sensitive in this way. Some may be sub- 

 jected for hours to the action of water at a high temperature, 

 or to steam, without the chlorophyll-corpuscles losing tlieir 

 structural character, whilst in others a few minutes suffices 

 to cause them to lose their form and to coalesce ; or, and 

 perhaps more usually, whilst retaining their individuality, 

 they swell internally and rupture, and then appear as irre- 

 gularly burst hollow spheres (fig. 3). The amount of starch 

 present in the chloroph) II- corpuscles determines to a certain 

 extent the rapidity of this effect. The more starcli present 

 the more certainly and the more easily will it be produced ; 

 but there are many tissues in which starch is present and 

 yet there is complete immunity from this action. This 

 rupturing of the chlorophyll-corpuscles, due to the starch, 

 must be distinguished from the exudation of colouring matter 

 and its accompanying substances already mentioned, which 

 is quite independent of the starch content, and is brought 

 about at a much lower temperature. 



The exudation of the coloured drops appears to be the 

 mechanical effect of a simple swelling of the ground-substance 

 due to its absorbing water, and it tliereby exercises a pres- 

 sure upon and squeezes it out, the vehicle holding the 

 colouring and other matters in solution which fills its 

 meshes. 



