DIPS IXTO MY AQUARIUM. 25 



one visit. I proceed, therefore, to single out two or three of the 

 objects seen, and separate them as far as possible from the rest. 



We will confine ourselves at present to the minute vegetable 

 organisms contained in the selected drop of water. The one-inch 

 objective has given us a magnification of about 50, but now let us 

 turn the nose-piece round and bring the -J-inch lens into position. 

 This is a glass constructed by the eminent opticians, Messrs. 

 Powell and Lealand, and it will give a magnification of over 300 

 with the B eye-piece of Ross. 



The first of these microscopic plants to which I shall draw 

 attention is a Desmid. Here is one, of which an illustration is 

 given (Fig. i), called Closterium. It is a familiar object, but in 

 this case familiarity does not breed contempt. Being of a bright 

 green colour, and full of chlorophyll, which requires the action of 

 sunlight, it follows that the proper time for collecting Desmids is 

 during Summer and Autumn, and they are generally found near 

 the surface of the water, wherejhe sun can get at them. 



Closterium striolatum. 



These pretty little plants lie almost at the very bottom of the 

 botanical scale. They belong to the natural order Algae, of which 

 sea-weeds are the best known types. But they are one-celled 

 Algae, and, as individuals, are invisible to the naked eye. They 

 are exclusively fresh-water organisms, and are never found in the 

 sea. In this they differ from their allies the Diatoms, which 

 thrive in both fresh and salt water. My experience leads me to 

 the conclusion that they are most easily found in shallow ponds 

 on open moors, and on damp bog-moss. If a bit of this bog- 

 moss {Sphagnum) feels slimy to the touch, the probability is that 

 we have come upon a crop of Desmids. When found, it is as 

 well to wash them into a glass bottle filled with clean water, where 

 they will soon settle on the sides and bottom, from which they 

 should be detached by a camel's hair brush, and deposited on a 



