OF THE ALGiE GENERALLY. 
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 outfiowings from a manufactory, 
or walls which have been moistened by the vapour issuing 
from a steam engine; for, in situations of this kind, ‘Algas 
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 Algge, 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 Diatomaceas 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 Desmidiaceje. 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 Alga3 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, CEdogonium fonticola, and 
Batrachospermum moniliforme developing themselves, 
