OF THE ALG.E GENERALLY; 6 



Green and brown excrescences on wood, slimy masses on 

 plants, pieces of wood and stone that have lain long under 

 water, layers of mud of a greenish or rusty brown colour 

 are things not to be passed by. Neither let him neglect to 

 examine such matter as the outflowings from a manufactory, 

 or walls which have been moistened by the vapour issuing 

 from a steam engine ; for, in situations of this kind, Algae 

 are often developed, which may otherwise be looked for in 

 vain except in hot springs. But, above all, the Algologist 

 should never forbear to collect an object under the suppo- 

 sition that he already possesses it. In the first place he 

 cannot be quite sure of this until he has placed it under 

 the microscope. Next to that, on the same batch of speci- 

 mens which have been collected early in the season, most 

 interesting parasites (as, for instance, Characium and 

 Hydrocytium) will often be found at a later period. 

 Lastly, it is actually necessary to examine certain species at 

 different times of the year, if the development and fructi- 

 fication are to be satisfactorily determined. Let it then be 

 an axiom with the collector of Algae, to take care to 

 gather always more, rather than less, than he actually needs. 



With regard to the fittest season for collecting water- 

 weeds it is sufficient to observe, that they are to be 

 obtained at all periods of the year, not excepting the 

 winter, many of the Diatomaceae showing themselves to 

 be perfectly indifferent to extreme changes of temperature. 

 At the same time increase takes place most largely in the 

 spring. On the other hand the autumn is the best time 

 for gathering Desmidiaceae. In fact, the periods of vege- 

 tation vary considerably. The species of Ulothrix, for 

 instance, occur only during the early months of summer, 

 and then vanish almost .entirely. Again it is requisite to 

 •observe, whether Algae are constant in any given spot, or 

 whether (as is often the case) they appear there for a 

 time only, and then disappear altogether. Thus I have 

 noticed Hildenbrandtia rosea, OEdogonium fonticola, and 

 Batrachospermum moniliforme developing themselves, 



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