SAPROLEGNIA 23 



Natural Key to the Species* 



SUB-GENCS ErsAPROLEGNiA; Eggs averaging more than two in an oogoniiiin, truly centric, 

 with a single layer of oil drops completely surrounding the protoplasm, or subcentric, 

 with two rows on one side and one on the other; oogonia with or without pits, smooth 

 or (in one species) with a few warts on some of the oogonia 

 DicUna Group: Oogonia not in chains or if so not tending to separate at maturity; their 

 walls not thick and the pits, if present, not very conspicuous; antheridia present, their 

 supporting branches at least in part long and branched 

 I. Antheridia present on about a third of the oogonia, diclin- 

 ous 5. cntstosa \ar. Ill (p. 70) 



1. Antheridia present on all or nearly all the oogonia 2 



2. Zoospores less than 20m thick 3 



2. Zoospores more than 20^ thick 6 



3. Antheridia all or mostly diclinous 4 



3. Antheridia all or mostly androgynous 5 



4. Spores not of two kinds 



Oogonial wall with few pits; eggs I2-22m thick 5. cruslosa van I (p. 69) 



Oogonial wall with few pits; eggs 17-27M thick S. crustosa van II (p. 69) 



Oogonial walls without pits (except where the antheridia touch); eggs 20-26^ 



thick 5. diclina (i) 



As above, but eggs averaging 30M thick 5. Kauffmaniana (2) 



Oogonial wall with numerous pits; eggs 12-22.5^ thick S. stagnalis (p. 70) 



Oogonial wall with less numerous pits; most of the eggs 25-27;^ thick. .S. delica (3) 



4. Spores of two kinds, large and small 5. anisospora (4) 



5. Oogonial stalks bent and often coiled; oogonial wall unpitted or the pits few and 



inconspicuous \ S. spiraUs {p. 7I) 



( S. f areata (p. 72\ 



6. Oogonia borne inside the host S. curvata (p. 72\ 



Ferax Group: Oogonia not in chains, or if so not separating at maturity; their walls 

 thick and usually with conspicuous pits; antheridia at times absent, but usually present 

 on a varying number of the oogonia; their supporting branches short, but not arising 

 from immediately below the oogonia. In 5. parasitica which probably belongs in this 

 group the oogonia are absent. 

 Antheridia not on all the oogonia (rarely over 50%), at times absent; androgynous 

 and diclinous 

 Antheridia usually on not more than 15% of the oogonia, often very few or 

 none; oogonia often found in old sporangia and then cylindrical; eggs com- 

 monly about 26m thick S. ferax (5) 



Antheridia absent; oogonia never or rarely cylindrical, eggs usually 21-24M 



thick 5. lapponica (p. 73) 



(See also 5. esocina (p. 41) 

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



usually 24-25M thick 5. mixta (6) 



As above but eggs usually 16-19^ thick S. mixta van Asplundii (p. 74) 



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



* The absence of oogonia in S. parasitica makes its position doubtful. For an artificial 

 key see below. American species are followed by a number, others by page reference. 



