158 THE LOWER FUNGI— PHYCOMYCETES 



(2) Some of the spores encysting in an irregular clump, 

 the others swimming away at once; secondary 

 sporangia usually developed as lateral branches 

 below the primary but sometimes formed by 

 proliferation. 



11. Protoachlya, p. 167 



2. Sporangia not clavate; oogonia usually 1-spored. 



a. Sporangium of very irregular and complex form; 



consisting of a much inflated branching basal portion 

 in which swarmspores are formed in several series, 

 and a slender elongate filamentous apical portion in 

 which they are cut out in a single row; the filamentous 

 portion acting as an exit tube through which all the 

 swarmspores pass; swarmspores encysting at the 

 mouth of the tube as in Aphanomyces. 



12. Plectospira, p. 167 



b. Sporangium cylindrical, thread-like; swarmspores 



arranged in a single row in the sporangium. 



(1) Swarmspores encysting at the mouth of the 



sporangium as in Achlya. 



13. Aphanomyces, p. 167 



(2) Swarmspores escaping separately as in Saprolegnia. 



14. Leptolegnia, p. 170 



1. Aplanes de Bary (1888: 650). 



This genus, as conceived by de Bary, is characterized by the 

 aplanetic nature of the sporangiospores, which, instead of leaving 

 the sporangium, germinate in situ by germ tubes. In other 

 essential respects the genus as described by de Bary resembles 

 Achlya. He founded the genus on a single species, Aplanes 

 androgynus (Archer) Humphrey (Fig. 55). This species is rela- 

 tively rare, and, though reported five times from various parts of 

 Europe, is as yet unknown from North America. The genus 

 has long been regarded as doubtful (Weston, 1919: 289), the 

 sporangia being extremely uncommon, and their behavior having 

 been variously described. 



In recent years Coker (1923: 76; 1927: 216) has considerably 

 modified the generic concept, and has included two additional 

 species, A. treleaseanus (Humphrey) Coker and A. turfosus 

 (v. Minden) Coker, representing transfers from Achlya and 

 Saprolegnia. He feels that observations made on the sporangial 

 stage of these three species have been too few and contradictory 

 to justify conclusions, but regards the sexual stage as distinctive. 

 The wall of the oogonium is said to be thicker than in other 



