422 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



KEY TO THE GENERA OF VAUCHERIACEAE. 



i. Filaments cylindrical. i. VAUCHKRIA. 



i. Filaments with frequent constrictions. 2. DICHOTOMOSIPHON. 



i. VAUCHERIA De Candolle, 1805, p. 61. 



Fronds filamentous, inarticulate, branches arising laterally 

 but often assuming a dichotomous appearance ; forming more or 

 less dense tufted or felty masses, usually attached by colorless 

 rhizoids ; numerous small chromatophores without pyrenoids, 

 and with very minute nuclei. Asexual reproduction by very 

 large zoospores, covered with cilia, with a small nucleus corre- 

 sponding to each pair of cilia ; produced in the somewhat cla- 

 vate ends of branches, partitioned off from the rest of the frond ; 

 germinating immediately ; by aplanospores produced usually at 

 the ends of short branches, arising similarly to zoospores, but 

 without cilia, germinating only after a longer or shorter period 

 of rest ; also in some species by akinetes, the filament break- 

 ing up into short portions, each with a thick wall. Sexual re- 

 production by oogonia and antheridia, of quite variable shape and 

 position ; usually on the same filament, but in some species on 

 distinct individuals ; oogonium sessile or pedicellate, partitioned 

 off from the frond and producing a large, globose, or subglobose 

 uninucleate oospore ; antheridium similarly located and parti- 

 tioned off from the frond, producing many biciliate spermato- 

 zoids, with cilia pointing in opposite directions ; when the 

 oospore is formed, the end of the oogonium dissolves, and the 

 spermatozoids enter, fertilizing the oospore, which germinates 

 after a resting period. 



A widely distributed genus of unattractive appearing plants, 

 but interesting by their elaborate and varied fructification. 

 Mostly fresh water species, they often extend into brackish 

 water, and some are strictly marine. Sterile plants are quite 

 indeterminable, and fruit is not always easy to find ; and in 

 dried material or herbarium specimens the fruit is not in as 

 good condition for study as in most other algae. 



KEY TO THE SPECIES OF VAUCHERIA. 



i. Antheridia not separated from the frond by an empty cell. 2. 

 i. Autheridia separated from the frond by an empty cell. 



PILOBOLOIDEAE. 14. 



2. Antheridia little or not at all curved. TUBUUGERAE. 3. 



2. Antheridia hooked or circinate. CORNICULATAE. 7. 



3. Oogonia spherical or nearly so. 4. 



3. Oogonia more or less ovoid or oblique. 5. 



