Wood.] -'•'^^ JiTiio 18, 



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

 spicuous forms are oscillatoria3 and zygnemaceee. The oscillatorise may 

 almost always be recognized 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 color, but is mostly dark ; dull greenish, blackish, purplish, blue, 

 &c. The oscillatorise are equally valuable as specimens at all times and 

 seasons, as their fruit is not known, and the characters defining the spe- 

 cies do not depend upon sexual organs. The zygnemas are the bright 

 green, evidently filamentous, slimy masses, which float on ditches or lie 

 entangled amongst the water plants, sticks, twigs, &c., in them. 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 naked eye with certainty whether 

 a zygnema 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 are 

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

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

 handsome masses of these algae are rarely worth carrying home. After 

 all, however, much must be left to chance ; the best way is to gather 

 small quantities from numerous localities, keeping them separate until 

 they can be examined. 



Adhering to the various larger ditch plants, to floating matters, twigs 

 and stones, &c., will often be found filamentous algae, which make fine 

 filmy fringes around the stems, or on the edges of the leaves ; or per- 

 chance one may meet with rivularise or nostocs, &c., forming little green 

 or brownish balls, or indefinite protuberances attached to small stems 

 and leaves. These forms are, however, to be looked for especially later 

 in the season. Whenever seen, they should be secured. 



In the latter part of summer-, there is often a brownish gelatinous scum 

 to be seen floating on ditches. Portions of this should be preserved, as it 

 frequently contains interesting nostocs and other plants. 



In regard to large rivers, the time of year in which I have been most 

 successful in such localities, is the latter summer months. Springs and 

 small bodies of clear water may be searched with a fair hope of reward at 

 any time of the year when they are not actually frozen up. I have found 

 some exceedingly beautiful and rare algae in such places as early as March, 

 and in open seasons they may be collected even earlier than this. The 

 desmids are most abundant in the spring, and possibly most beautiful 

 then. They, however, rarely conjugate at that time, and the most valua- 

 ble specimens are therefore to be obtained later — during the summer and 

 fall months ; at least, so it is said ; and the little experience I have had 

 with this family seems to conflrm it. Bivuleis should be watched espe- 

 cially in early spring, and during the summer months. 



I 



