98 THE SAPROLEGNIACEAE 



Achlya deBaryana {A. polyandra deB.). typical form: Wall not pitted: antheridial branches 



almost always androgynous, but ne\er arising from oogonial stalks, much branched, 



not winding about the hyphae; eggs small (18-26/1) and numerous. 

 Achlya deBaryana, Horn's form: Wall not pitted (except in certain chemicals); antheridial 



branches mostly diclinous, but also androgynous, long and branched; eggs small, few 



(1-5, usually 2 or 3 normally: in peptone up to 20). This is nearest A. imperfecta 



and is probably the same. 

 Achlya Orion: Antheridia practically all androgynous, present on about 75% of the oogonia; 



eggs usually I or 2, most about 33-36^ thick. 

 Achlya prolifera: Wall pitted; antheridial branches all diclinous, much branched, winding 



about h>phae; eggs small, rather numerous. 

 Achlya aplanes: Wall with or without pits; antheridial branches long and branched, all 



diclinous; eggs rather few, large (24-31.5/1); spores emerging as usual or remaining 



in the sporangium, in either case without a swimming stage. 

 Achlya proliferoides: Wall pitted; antheridial branches mostly diclinous, long and much 



branched, winding about hyphae; eggs small, few, mostly failing to mature. 

 Achlya flagellata: Wall pitted; antheridial branches more often diclinous than androgynous, 



perhaps about three times as often but varying in this respect, long and much branched; 



eggs large, of moderate number. 

 Achlya imperfecta: Wall pitted; antheridial branches as often androgynous as diclinous, 



frequently long and much branched, not winding about the hyphae, often arising from 



the oogonial stalks; eggs few, small, mostly failing to mature in our form (this point 



not mentioned by Minden). 

 Achlya Klebsiana: Wall not pitted; antheridial branches all diclinous, long and much 



branched (apparenthO, not wrapped about the hj'phae; eggs of moderate size and 



number. 

 Achlya caroliniuiia: Wall not pitted; antheridial branches absent; eggs few, small. 



Natural key to the Species of Achlya* 



Sub-genus Cextroachlya: Eggs truly centric with a complete circle of small droplets sur- 

 rounding the protoplasm in .1. racemosa, A. colorata, and .1. hypogyna, subcentric 

 in A. radiosa.'\ Antheridia present in all but one species, androgynous, borne on 

 short and usually simple or little branched threads which arise in great part from 

 the oogonial stalks (except in one species). Oogonial walls yellow. Sporangia 

 typically cylindrical or slightly thicker near the tip; spores not forming a hollow 

 sphere on emerging (in Chapel Hill species). 

 Racemosa Group: The only group of the sub-genus and similarly defined 



Oogonia smooth; eggs commonly about 22m thick A. racemosa (2.) 



Oogonia more or less thickly set with blunt or short papillae or spines (a part 

 of the oogonia sometimes smooth) 



Hypogyna! cell often present A. hypogyna (l) 



Hypogynal cell absent 



Antheridia on all the oogonia, and nearly always arising from the stalk, 



eggs usually 1-4, their diameter as a rule 30-37M A. colorata (3) 



Antheridia on all the oogonia, arising from their stalks or from the main 

 threads; eggs i (rarely 2 or 3), their diameter usually 34~37m 



.4. radiosa (p. 139) 



*The position of .1. Iloferi is entirely conjectural until the structure of the eggs is 

 known. It is therefore omitted from the following scheme. For artificial key see p. 104. 

 American species are followed by a number, European by a page reference. 



f The structure is not accurately known in the other species. 



