19^2 



Collecting and Preserving Fresh Water Alg^. 

 Bj Dr. Horatio Wood, Jun.* 



There are three or four distinct classes of localities, in each of 

 which a different set of forms may be looked for. These are 

 stagnant ditches and pools, springs, rivulets, large rivers, and other 

 bodies of pure water, dripping rocks in ravines, &c. ; trunks of 

 old trees, boards, branches and twigs of living trees, and other 

 localities. 



In regard to the first — stagnant ivaters — in these the most con- 

 spicuous forms are Oscillatori^ and Zygnemacc^. The Oscilla- 

 toriae may almost always be recognised at once by their forming 

 dense slimy strata, floating or attached, generally with very fine 

 rays extending from the mass, like a long, delicate fringe. The 

 stratum is rarely of a bright green colour, but is mostly dark, dull 

 greenish, blackish, purplish, blue, &c. The Oscillatorias are equally 

 valuable as specimens at all times and seasons, as their fruit is not 

 known, and the characters defining the species do not depend upon 

 sexual organs. The Zygnemas are the bright green, evidently 

 filamentous, slimy masses, which float on ditches, or lie in them, 

 entangled amongst the water plants, sticks, twigs, &c. They are . 

 only of scientific value when in fruit, as it is only at such times 

 that they can be determined. Excepting in the case of one or two 

 very large forms, it is impossible to tell with the nalced eye with 

 certainty whether a Zyghema is in fruit or not ; but there are one 

 or two practical points, the remembrance of which will very greatly 

 enhance the probable yield of an afternoon's search. In the first 

 place the fruiting season is in the spring and early summer, the 

 latter part of March, May, and June being the months when 

 the collector will be best repaid for looking for this family. Again, 

 when these plants are fruiting they lose their bright green colour 

 and become dingy, often yellowish, and very dirty looking — just 

 such specimens as the tyro would pass by. The fine, bright green, 



* Extracted from " A Contribution to the Natural History of the Fresh Water 

 Algas of America." Washington, 1873. 



