OF THE CHARACTERISTICS OF THE DIATOMACE.E. 



CHAPTER V. 



OF THE CHARACTERISTICS OF THE DIATOMACE^. 



Before concluding my remarks on the Diatomace^e I wish 

 to call the attention of the reader to the principal charac- 

 teristics by which they are distinguished from other mem- 

 bers of the vegetable kingdom. These are their form and 

 the curious markings of their silicious coats ; and with 

 these, varying as they do in the most extraordinary 

 manner, the botanist should make himself thoroughly 

 acquainted. 



With regard to the form of the plant, he must not be 

 content with a single view of the individual, however 

 favourable it may seem. Whichever side is turned towards 

 him, when the specimen is first placed under the lens, his 

 first object should be to roll and turn it on the slide, in 

 such a manner as to expose the other side also to view. 

 This is a difficult business with many of the species (those, 

 for instance, of Fragilaria) which are propagated in long 

 ribbon-like filaments, and which, from the flatness of their 

 outline, lie close against the glass. He must be prepared, 

 indeed, to give up a good deal of time, and to exercise no 

 little patience, before he accomplishes his obj ect ; but 

 practice and experience are sure to bring success in the 

 end. 



As the language in which authors describe the two 

 aspects under which every Diatomaceous Alga ought to be 

 viewed is often obscure, the reader may get a good notion 

 for himself by the inspection of an ideal figure like that 

 which is here annexed, fig. 45. It represents a column or 

 cylinder, divided into several parts, and, by naming the 



