AClllAA 101 



,^. Eggs small, averaging less than 2t,m in diameter 4 



.^. Eggs larger, averaging more than 23^ in diameter 5 



4. Oogonial walls pitted; antheridial branches arising from the main hyphae between and 



near the oogonial branches A. americana (6) 



4. Oogonial walls unpittcd (except where the anlheridia touch); antheridial branches 



arising from the oogonial branches, sometimes from the base of the oogonium; egg? 



centric A. racemosa (2) 



4. Oogonial branches not long, oogonial wall unpittcd; eggs eccentric, about 18-25^ 



thick, usually ,^-lo; antheridial branches rather long and branched, arising as a rule 

 from the main hyphae (rarely from the oogonial stalks also) ; antheridia on all oogonia 



A. deBaryana (p. 141) 



5. Oogonial branches about as long to twice as long as the diameter of the oogonia or some 



even longer; oogonial wall strongly pitted; most eggs about 25^1 thick; antheridia 



on all or nearly all oogonia A. conspicua (17) 



5. Oogonial branches much longer than the diameter of the oogonia; oogonial wall unpitted ; 

 eggs subcentric (?), about 27/j thick, 5 to 25 in an oogonium; antheridia on all oogonia 

 from branches which arise as a rule from the oogonial stalk.....-!, polvandra (16) 



5. Oogonial branches much longer than the diameter of the oogonia; oogonial wall un- 



pitted; eggs eccentric, usually 1-2 in an oogonium, most about 33-36^ thick 



A. Orion (7) 



6. Oogonial wall pitted - 



6. Oogonial wall unpitted (except in one case in certain chemicals) 9 



7. Antheridial branches always diclinous, much branched and winding like a parasite 



about the oogonia; eggs small (20-26^1), numerous A. prnlifera (14,^) 



7. Like the above, but eggs larger (24-31. 5/i) and spores said to be without a swimming 

 stage A. apiaries (p. 143) 



7. Antheridial branches diclinous and androgynous 8 



8. Antheridial branches mostly diclinous, in many cases winding themselves about the 



main hyphae A. proliferoides (8) 



8. Antheridia more often diclinous than androgynous, not winding about the hyphae and 

 never arising from the oogonial stalks A. flagellata (()) 



8. .Antheridial branches about equally androgynous and diclinous, usually long and much 



branched but not winding about the hyphae, not rarely arising from the oogonial 

 stalks A. imperfecta (10) 



9. Antheridial branches all diclinous; oogonial wall unpitted; eggs numerous 10 



0. Antheridial branches all diclinous; oogonial wall unpitted; eggs few; sporangial wall 



often disintegrating ,4. diibia (21) 



0. Antheridial branches mostly androgynous; eggs 2-8 A. megasperma (15) 



10. Oogonia oval to pyriform (in a variety globular); eggs numerous, usually about 15. 



averaging 23M thick (27M in Humphrey's form) A. oblongata (18) 



10. Oogonia round, their stalks short; eggs averaging 10-15 in an oogonium, and 27M thick 



A. oblongata var. globosa (19) 



10. Oogonia round or slightly oval, the stalks short; eggs 4-10 in an oogonium, averaging 



about 25m thick A. Kkbsiana (11) 



1 1. Oogonia without antheridia 12 



1 1. Oogonia (at least in part) with antheridia 13 



12. Oogonia spherical or elliptical; eggs 1-4, about 29/1 thick A. cornuta (5) 



12. Oogonia oval; eggs numerous, generally about 20, averaging 20m thick; parasitic on 



fish A. Iloferi (p. 145) 



12. Oogonia spherical; eggs few, usually 1-2, not rarely 4, 22^ thick .1. caroliniana (12) 



