On Staining and Mounting Wood Sections. By M. H. Stihs. 133 



have received the following letter this morning in reference to the 

 present paper, which I am privileged to insert here : 



" OSPRINGE ViCAEAGE, FaVEESHAM, 



12 Januanj, 1876. 



" Dear Dr. Koyston-Pigott, — In the enclosed paper, on which 

 you encourage me to express an opinion, I see nothing to modify 

 or alter. I understand your view to he this. The hooks treat of 

 chromatic aberration as if there were no spherical aberration. This 

 is hypothesis which nature does not accept. Therefore the true 

 and exact way is to examine an exterior ray in its entire 

 straggHng— 



'• (1) From the geometrical focus in virtue of what we call 

 spherical aberration. 



"(2) From its fellow constituents of the unrefracted ray of 

 white light in consequence of chromatic aberration. 



" Both of these demand consideration as coexistent causes of a 

 pencil not converging exactly to a point. 



"This you seem to me to have accurately expressed in the 

 paper which I now return. 



" Believe me to be faithfully yours, 



"W. N. Griffin." 



I have received letters from equally distinguished mathe- 

 maticians, approving of my first paper on this subject, which I 

 have placed in the hands of our Honorary Secretary, Mr. Slack. I 

 am allowed to add that Mr. Grifiin approves the first paper also, 

 as containing " nothinsr inaccurate in its statements." 



ly. — On Staining and Mounting Wood Sections. 



By M. H. Stiles. 



The staining of sections of vegetable tissues so greatly assists the 

 microscopist who engages in the study of their structure, that any 

 improvement in the preparation and mounting of such sections will, 

 I feel sure, be eagerly welcomed. 



During the past few months I have made many experiments in 

 connection with this subject, and the results obtained are so good, 

 and the method so simple, expeditious, and, in some respects, new, 

 that I think I shall be justified in pablishing a short outhne of it. 



The cutting of sections of woody or herbaceous stems and roots 

 does not usually present much difiiculty ; simple maceration in cold 

 or tepid water, or, in the case of some dried specimens, in a mix- 

 ture of equal volumes of spirit of wine, glycerine, and water, will 



