THE GREEN ALGAE OF NORTH AMERICA 267 



There is no danger of mistaking a Bulbochacte, even in the 

 sterile condition, for any other alga ; the erect, branching frond, 

 with cells larger at their top than at their bottom, and every 

 branch ending in a long seta with a bulbous base, are unmis- 

 takable characters. In the determination of species much the. 

 same distinctions are used as in Oedogonium^ and also charac- 

 ters drawn from the formation of the oogonium ; as this arises 

 by a double division of the vegetative cell, the suffultory cells 

 are two, and according as the upper of the two is longer or 

 shorter than the lower, or of the same length, we have the char- 

 acters, dissepiment inferior, superior or median. If the two 

 partition walls have formed directly across the axis of the orig- 

 inal cell, we have oogonium erect ; if one of them is oblique, 

 giving one of the cells a five-angled appearance in section, we 

 have oogonium patent. 



The species of Bulbochaetc are found in the same stations as 

 Ocdogonium, and though not so common as species of the latter, 

 they are by no means infrequent, and are distributed all over 

 the world. 



KEY TO THE SPECIES OF BULBOCHAETE. 



i. Spores globose. 2. 



I. Spores ellipsoid. 10. 



2. Oogonia erect. i. B. Brebissonii. 



2. Oogonia patent. 3- 



3. Oogonia 60 /j. diam. or more. 4- 



3. Oogonia not over 56 /n diam. 5- 



4. Gynandrosporous. 8. B. setigera. 



4. Idioaudrosporous. 18. 

 5. Oogonium biconic- or subquadrangular-globose. 7. B. augulosa. 



5. Oogonium depressed- or subdepressed-globose. 6. 



6. Dissepiment of suffultory cell about median. 7. 



6. Dissepiment of suffultory cell superior. 



7. Membrane of oospore minutely crenulate. 2. B. intermedia. 



7. Membrane of oospore strongly creuulate. 3. B. crenulata. 



8. Oogouia 44-56 A* diam. 6. B.dispar. 



8. Oogonia rarely equalling 46 M- 9- 



9. Gynandrosporous. 4- B. Nordstedtii. 



9. Idioandrosporous. 5- B. polyandria. 



10. Monoecious. IT - 



10. Dioecious. T 3- 



