12 MICROSCOPICAL EXAMINATION 



I trust this article will give the members a clear appreci- 

 ation of what aperture means, and the mode of expressing it 

 numerically ; also what increase of resolving power may be 

 expected to be obtained from an increased aperture. 



On the flDicro0Copical Eyamination of 

 Cbloropb^ll, SniUin, anb protein^Ci^stale, 



Translated FROM the German of Dr. Leopold Dippell. 

 By Chas. Vance Smith. 



CHLOROPHYLL, the green colouring matter of plants, 

 consists, strictly speaking, of a formless substance, and 

 only takes the shape of grains, when it serves to impreg- 

 nate other constituents of the contents of the vegetable cell, 

 v/hich are then termed Chlorophyll-bodies. It never forms the 

 contents of minute vesicles, as has been asserted on insufficient 

 evidence. To ascertain its amorphous character, it is only 

 necessary to place a suitable section in either alcohol or ether, 

 which will at once dissolve out the Chlorophyll, leaving the base, 

 which it has served to colour, behind unchanged. 



In the case of many plants — for example, the cells of 

 Drapariialdia^ Spirogy?'a, Zygnema, Closterium^ anci other algas, 

 and also in the fronds of AntJioceros — the Chlorophyll is distri- 

 buted indiscriminately through the general protoplasm, and may, 

 for distinction sake, be spoken of as amorphous. In by far 

 the greater number of plants, however, it is not thus generally 

 distributed, but is confined to certain granular bodies imbedded 

 in the protoplasm, and has the api)earance of being itself 

 granular. 



The matter of which these Chlorophyll bodies is composed 

 is not the same in all plants, being, in f^ict, of two kinds. In the 

 first, they consist of a nitrogenous substance, probably a hardened 

 portion of the protoplasm ; since, on withdrawing the colouring 

 matter by means of alcohol or ether, and applying the usual 

 chemical tests, an unmistakeable albuminous action is evident. 

 Such Chlorophyll-grains are found in the fully-developed leaves 



