PROCEEDINGS OF THE SOCIETY. 263 



Mr. Gordon's question as to what degree of accuracy was obtainable by 

 his arrangement, he was unable to say exactly, not having given special 

 attention to the point. The question was obviously one as to whether 

 ;any practical difficulty presented itself in connection with the construction 

 of the apparatus proposed, or in connection with the making of the 

 necessary observations. With regard to the latter point, it would, he 

 thought, be clear to everyone who tried the apparatus that there was 

 no difficulty in making the readings with exactness. With regard to 

 the former point, he would only say that, working as he had been doing 

 with diffraction gratings constructed by Messrs. Sanger Shepherd, and 

 with an eikonometer constructed by Messrs. Beck, he had found the 

 error in the measurements he had made was one which might be 

 altogether neglected. He had no doubt that the ground-glass screen 

 which had been suggested by Mr. Conrad Beck would get over any 

 difficulty in the matter of depth of focus, but he had not had practical 

 experience of such a difficulty. He still, after hearing Mr. Beck, was of 

 opinion that the balance of practical convenience was in favour of the 

 method of ascribing a fixed magnifying power to the objective, and a 

 variable magnifying power to the ocular in the case where the tube-length 

 was subject to modification. 



The President then proposed a hearty vote of thanks to Prof. 

 Wright for his extremely important and interesting communication, 

 which being put to the Meeting was carried unanimously. 



A Note by Mr. E. B. Stringer, ' On the Separation of Ultra-Violet 

 Light,' was read by Dr. Hebb. 



On the motion of the President, the thanks of the Society were voted 

 to the author. 



Mr. A. Platters exhibited upon the screen a series of about sixty 

 hand-painted lantern slides illustrating botanical histology. These slides 

 were photomicrographs taken from the actual sections under the Micro- 

 scope, and coloured to represent the results of staining ; the great beauty 

 of many of the sections shown, and the fidelity and accuracy of the 

 colouring, were greatly admired and appreciated by the Meeting. 



The President said that anyone who, like himself, had spent a good 

 deal of time over the anatomy of plants, could not fail to be greatly 

 pleased with this extremely interesting exhibition. A number of points 

 of great botanical interest had been brought before them. The sections 

 from which the slides were taken must have been exceedingly good ones, 

 and the manner of showing the effect of double staining was most 

 successful. The accurate colouring of the photographs must require not 

 only great skill, but also considerable botanical knowledge. He noticed 

 one section in which the cambium appeared to have taken up a different 

 stain from the phloem, and he should like to know how this result was 

 obtained ; he should also like to ask under what circumstances the false 

 annual rings shown in a slide of pines were produced. The most 

 beautiful of the whole series was certainly the one showing the pollen- 



