THE DESMIDS. 



349 



come, it dies, breaks away, and passes down the river, to grow again 

 and run the same course next year. 



There are other confervae in the river, such as the one magnified 

 50 diameters (fig. 799), but enough have been figured 

 to show generally the characters of this class of 

 vegetation. Towards autumn a curious process takes 

 place with the confervoid filaments ; two parallel 

 fibres send out processes and unite together. This 

 is called conjugation (fig. 806), .and has some sin- 

 gular effect upon the cells of the fibres themselves, 

 which results in a discharge of spores, from which 

 the plant is reproduced the next year. The engraving 

 is taken from a drawing by the late eminent microscopist Mr. 

 Quekett. 



Fig. 8o6l — Conjugation 

 of Confervas. 



After the Algae we have plants of much interest and great 

 microscopical beauty, called Desmids. These are not very numerous 

 in my garden, as they prefer little pools the temperature of which is 

 higher than in my streams ; but we 

 have some six or seven species in small 



quantities : the character of our water fig. soz.-ciosterium Leibkinu, x 150 diam 

 evidently does not suit them. Their use in the great scheme of 

 creation is unknown. I have given the figure of Closterium Leibleinii 

 (fig. 807) as an example of this kind of plant life. 



After the Desmids there is an extraordinary group of plants called 

 Diatomes (figs. 808 to 814), of which systematic writers make many 

 genera, which literally abound in my garden. If we look one day 

 at our rippling brooks, the pebbles are as bright as the ornaments 

 in a well-kept drawing-room, but if we look a few days afterwards they 

 are covered apparently with dirt and slime. Not so, however ; that 

 seeming dirt and slime is vegetal organism, replete with interest, and 

 is called a diatome. Some persons have considered these plants to 

 belong to the animal kingdom, so obscure is their purpose, but all 



