PEOOEEDmGS OF SOCIETIES. 55 



but would just observe that all who were in the habit of using a 

 concentric stage, especially with high powers, were aware how difficult 

 it was always to keep the object in view, in consequence of some very 

 slight difference between the centering of the stage and the objective ; 

 even a jar would sometimes alter an objective in this respect, so that 

 one which was perfectly true when sent out by the maker might be 

 thrown out by being thrown down roughly in carriage. The addition 

 to the microscope exhibited was designed to enable any person to 

 centre the stage accurately to the object he was using. 



Mr. Charles Brooke thought this was a very good idea for effecting 

 a very useful purpose. He had frequently met with the difficulty 

 which it was designed to obviate, and believed it most frequently 

 arose from the screw not being exactly central, and in which minute 

 differences — far more minute than any practical mechanism could 

 overcome — would be enough to cause a very appreciable error in the 

 case of a high power. He believed that it was a circumstance which 

 no ingenuity could overcome, and that no centering, however carefully 

 arranged, would under all circumstances be found perfect. 



The thanks of the meeting were voted to Mr. Crouch for bringing 

 the improvement before their notice. 



Mr. Alfred W. Bennett read a short paper relative to certain 

 organs wliich he had observed on the leaves of Drosera and other car- 

 nivorous plants, and to which he had lately drawn attention in the 

 'Popular Science Review.' The subject was illustrated by numerous 

 preparations exhibited under the microscope. (The i>aper will be 

 found printed at p. 1.) 



The President, in proposing a vote of thanks to Professor Bennett 

 for his communication, inquired if there was a definite relationship 

 observed between the characters of the tropical plants which had 

 these glands, and those which were allied to Drosera. 



Mr, Slack said these objects were evidently quite distinct from 

 those which belonged to Coleus, which seemed to be only modifi- 

 cations of glandular hairs. In Coleus the stems on which these 

 glands were erected were very short, but in others, such as Lavender, 

 they were long stems with knobs on the top. On Coleus there was 

 a distinct cross, like a hot-cross-bun mark, indicating a tendency to 

 divide. He happened to have a slide of a piece of Digitalis leaf 

 from Calcutta, in which there was a complete division, forming a 

 cross of four cells. The internal glandular objects described by 

 Professor Bennett evidently had quite another function. 



Mr. Bennett said he had frequently observed these structures im- 

 bedded in the leaf immediately beneath the tentacles. They were not 

 hair structures in any sense of the term. 



The President called the attention of the meeting to the fact that 

 a post-card had been received from Germany, addressed to Mr. Hard- 

 wicke, saying that Herr Moller's proposed work on the Diatomaceee 

 would not be published. 



Mr. Beck said he had also received a communication of the same 

 kind, and inferred that the number of subscribers for the work was 

 deemed insufficient, and that therefore it would not be brought out. 



