26 THE SAPROLEGNIACEAE 



10. Antheridia absent; oogonia never or rarely cylindrical, eggs usually 21-24/1 thick 



5. lapponica (p. 73) 



See also 5. esocina (p. 41) 



10. Antheridia usually on about half the oogonia which are never cylindrical; eggs mostly 



:4-25m thick 5. mixta (6) 



10. As above, but eggs mostly only 16-19/1 thick 5. mixta var. Asplundii (p. 74) 



10. Antheridia on about 75% of the oogonia 5. floccosa (p. 74) 



I. Saprolegnia diclina Humphrey. Trans. Am. Phil. Soc. 17: 109, pi. 



17, figs. 50-53. 1892 [1893J. 

 Saprolegnia dioica deBary. Bot. Zeit. 46: 619, pi. 10, figs. 12 and 13. 



1888. 

 Not S. dioica Pringsheim or 5. dioica Schroeter (which see under 



5. ferax and 5. mixta). 



Plates 3, 4 and 14. 



Main hyphae of moderate size and length, little branched. Spor- 

 angia only slightly enlarged and broadest near the end, repeatedly 

 proliferating inwardly, but also not rarely arising laterally from beneath 

 the discharged ones, as in Achlya. Spores 11-11.551 in diameter. Gem- 

 mae very abundant and variable in shape, long and pointed or stocky 

 and knotted, the longer ones rather characteristic for this species, the other 

 forms much as in S. delica, etc. By single spore cultures made several times 

 the species has proved to be not dioecious (heterothallic) although highly 

 diclinous, the mycelium from a single spore producing both oogonia and 

 antheridia. Oogonia spherical or oval or pear-shaped, usually with a short 

 neck, mostly terminating the main branches, but not rarely intercalary, 

 occasionally two or three to five in a chain, rarely on short lateral branches 

 or cylindrical in empty sporangia, very variable in size, even in the same 

 cultures, 35-iooyi in diameter; walls rather thin, without pits except where 

 the antheridia touch. Antheridial branches arising diclinously from near 

 or distant hyphae, branching, delicate, slender, and soon disappearing after 

 the antheridia have been cut off. Antheridia on every oogonium, numerous, 

 often completely covering the oogonium, usually slender and not much 

 larger than the branches, occasionally somewhat swollen and tuberous, 

 only moderately dense, but remaining visible for a long time after the 

 antheridial branches have disappeared. Antheridial tubes nearly always 

 invisible (if present). In only two cases were they seen. (But see below 

 for Trow's statement as to fertilization.) Eggs 20-261J. in diameter, most 

 about 23-24[j., varying little in size in any one oogonium, one to twenty 

 or more in an oogonium, usually six to twelve, centric. 



Common in branches and small streams, such as Arboretum brook, 

 Battle's brook, branch back of athletic field, etc. Collected in Chapel 

 Hill 76 times between February 29, 1912, and December 16, 1913 (see 

 table), and found many times since. 



