S6 



AN HOUR AT 



I think it much the best, after taking the shdes carefully out 

 when the box arrives, to place them in a shallow tray ; which may 

 be easily made out of card, or a draper's box answers the purpose 

 admirably. There they can remain, taking up each sei'iatim for 

 examination and comparison, until the time arrives for packing up 

 and sending off again. In this way, too, any links of connection 

 between the various slides will be readily seen ; and fresh ones, not 

 at first perceived, will occasionally suggest themselves. Some 

 members appear to place them in a cabinet, amongst their own 

 slides, which, however, involves the risk of troublesome admix- 

 ture unless there be a vacant drawer which can be utilised, for the 

 time being. Marking on the labels of the slides themselves to 

 prevent any confusion of this kind I have several times noticed, 

 and consider quite an unwarrantable liberty. 



We are all greatly indebted to the Rev. J. M. Mello for the 

 opportunity of inspecting, from time to time, his illustrations of 

 Micro-Petrology (Pk 2, Figs, i, 2, 3). May I venture, on behalf of 

 those who have not worked so deeply at this interesting, yet novel, 

 branch of research as he has done, to ask him to make his terms 

 as simple as may be, and to explain the meaning of such as it 

 appears requisite to use ? " Orthoclase," " Twin-Crystals," 

 " Quartz porphyritically developed," " Oligoclase," " Oliogo- 

 clastic," and "Sanidine," may be taken to illustrate what I 

 mean. With every desire to gain all that may be learnt from 

 examination of his slides, and after spending many hours of 

 valuable time in hunting over books likely to help, with various 

 detached papers, I have to confess inabiHty to comprehend the 

 meaning of all of them, so as to get a lucid picture of what they 

 put before us. 



The chalky whiteness to be often seen at the enlarged base of 

 the hairs of Vegetable-Marrow leaf is doubtless due to the 

 presence of Carbonate of Lime in the cells, as has been 

 shown by Professor Gulliver to be the case with a similar appear- 

 ance in the leaf-hairs of Viper's Bugloss ( Lycopsis arve?isis). It 

 would be easy to try this by tearing part of a mature leaf to pieces 

 on a slide, adding acetic acid, and then watching for the appear- 

 ance of effervescence. Although the Cell-coiUcnts are so different, 

 the structures by which these hairs are built up are nearly the 

 same as with the Nettle tribe ; whereupon Lindley has some 

 interesting remarks on relationships between these two Natural 

 Orders, otherwise apparently so remote (Lindley's Vegetable 

 Kingdom i7i loco). It is easy to make a little confusion between 

 the scattered whiteness visible in the decaying leaves of Vege- 

 table-marrow, which is caused by these hairs, and that which is 

 due to the overspreading of an Oidium, a form of fungus undis- 



