QUEKETT MICROSCOPICAL CLUB. 95 



number of tubes and bottles required becomes inconvenient 

 and subject to disaster by breakage. Under these circumstances, 

 therefore, the author had adopted the plan of killing and fixing 

 the desmids where they were collected, and he had found this 

 quite satisfactory. The method is as follows : A small funnel 

 to support filtering material is essential. It was found that the 

 best material for the filter was chamois leather, which has the 

 advantage that it allows of the residue left, after the water 

 has run off, being scraped up with a spatula without risk of 

 tearing the filtering material. The filtered residue may then 

 be placed in tubes (3-in. by 1-in. is a convenient size), each 

 numbered to correspond with notes giving the name of the 

 locality and the habitat, as bog, moor pool, pond, etc., with any 

 other desired particulars. When what is deemed a sufficient 

 amount has been placed in the tube, this should be nearly filled 

 with clear water and about 4 cubic centimetres of the following 

 killing and fixing solution should be added : 



Cupric sulphate (10 per cent, solution) . . , 100 c.c. 



Mercuric chloride (saturated solution) ... 10 c.c. 



Extreme accuracy in the quantity added is not necessary, 

 and a little practice soon enables one to estimate the right amount. 

 The only drawback connected with this method of treatment is 

 that the material is apt to become too concentrated. Care, 

 therefore, should be taken not to place too much in a tube. 

 As in about 10 cubic centimetres of filtered material obtained 

 from one small unimportant bog over one hundred species and 

 varieties of desmids were found, it is obvious that this is a very 

 practical and productive method. Large, old-established bogs 

 yield the best results, both as to individuals and species, and 

 bogs which form during the winter and dry up in the summer 

 should be avoided ; they are seldom remunerative. Moorland 

 pools are always w^orth the collector's attention, and often yield 

 quite different species from those of the bogs. A feature that 

 strikes one in connection with them is that often they are occu- 

 pied almost exclusively by one, or at most a very few, species. 

 One moorland pool examined on Dartmoor was so filled with 

 Staurastrum hrachiatum that from every part of it the net was 

 crowded with specimens, and another small pool was quite 

 green with the rod-like threads of Hyaloiheca dissiliens, and 



