848 AQUATIC PHYCOMYCETES 



DICTYUCHUS Leitgeb 



Bot. Zeitung. 26: 503. 1868 



(Fig. 65 L-M, p. 836) 



"Mycelium usually quite vigorous, reaching a diameter of 2-3 cm. 

 on hempseed; threads branched, up to 100 \x thick at the base, straight 

 at first except where branched, becoming eventually quite zigzag by the 

 continual formation of apical sporangia from the base of which the 

 thread continues its growth. Sporangia formed in great abundance, at 

 first around the outer margin of the culture, later scattered over the 

 entire surface; first sporangia long-cylindric, often thicker in the distal 

 half than in the proximal; sporangia in the D. monosporus group with 

 spores included, in large part breaking away from the hyphae and 

 floating on the surface of the water ; the greater part of hyphae often 

 becoming sporangia, even including the oogonial and antheridial 

 branches ; sporangial wall persistent in the D. monosporus group, quickly 

 disappearing in the false-net group, but the encysted spores sticking 

 together to retain the sporangial shape; spores encysting within the 

 sporangia, emerging later in the laterally biciliate form, leaving their 

 empty cysts in the form of a true or false net; primary sporangia in 

 some species of the Achlya type. Gemmae lacking or, in one species, 

 rarely present. Plants heterothallic, homothallic, parthenogenetic, or 

 apparently sexually sterile. Oogonia when present with a single eccentric 

 egg" (Coker and Matthews, 1937). 



Type species: Dictyuchus monosporus Leitgeb. 



TAXON NOT IN COKER (1923) OR COKER AND MATTHEWS (1937) 



Dictyuchus pseudoachlyoides Beneke 

 J. Elisha Mitchell Sci. Soc, 64: 263, pi. 30, figs. 1-13. 1948 



BREVILEGNIA Coker and Couch 



J. Elisha Mitchell Sci. Soc, 42: 212. 1927 



(Fig. 65 NO, p. 836) 



"Mycelium depauperate, dense and opaque, never aerial. Sporangia 

 in the great majority behaving about as in Thraustotheca, the wall soon 



