BURGESS : PIGMENT CELLS OF PLANTS. 



61 



varying the light used in illuminating the object, are seen to be more 

 transparent than the other parts of the cells and if viewed under 

 polarized light are seen much more distinctly. 



In bringing this paper to a close I must say a few words on the 

 examination of objects. It is well I find to use almost every power of 

 magnification we have, in turn, as one object glass will sometimes shew 

 one thing, and another object glass will bring out another ; again the eye 

 pieces may be also varied, using a deep eye piece with a low power, and 

 a low eye piece with a high power, and again both high powers in the eye 

 piece and object glass together, and again low eye pieces and low powers 

 in the object glass together. Then as to illumination, this can be changed 

 and changed about, one while using the object as a transparent one, 

 then again as an opaque one, also with the parabola, angular light, 

 excess of light, almost total absence of light, and many other ways, each 

 of these may be made to yield some extra facts in the school of exami- 

 nation. 



And last the most of all importance — Polarized Ligrd. I cannot 

 say too much about this, its merits having been greatly overlooked — I have 

 for a long time considered that unless I have used polarized light upon any 

 object I have had in hand for examination, that I had only partially 

 seen it, and I would advise all our friends to follow out the same course, 

 and then I dare predict much greater knowledge on every subject will be 

 the sure result — so far as the Pigment Cells of Plants are concerned, 

 they do not owe much to Polarized Light for enhancing their beauty, but 

 still I can fearlessly assert I should not have been able so clearly to state 

 many of the facts contained in this paper but for the use of it, — and to 

 any of our friends who may care to investigate the nucleus, with a view 

 to find out its nature and use. Polarized Light at once tells us, in unmis- 

 takeable language the way by which this can be ascertained. 



I regret that so little can be done in a short paper like this, but 

 should this have proved to be of any interest to our friends generally, I 

 may then perhaps be allowed to say they may take this as a first instal- 

 ment of a debt which, let us all feel individually we owe, to the Queckett 

 Microscopic Club. 



