162 THE LOWER FUNGI— PHYCOMYCETES 



(1926: 140) and a variety T. unisperma var. UtoraliH Coker & 

 Braxton (1926: 141) have been transferred to Brevilegnia (Coker 

 1927:213). 



3. Calyptralegnia Coker (1927: 219). 



This most recently described genus of the family is based on a 

 single species, C. achlyoides, which had been described earlier 

 as Thraustotheca achlyoides Coker & Couch (1923: 112). The 

 species was isolated from the soil. Though it is not in all 

 respects a typical Thraustotheca it would seem to fall very near 

 that genus, and its removal will be questioned by some students. 



In Calyptralegnia, as the genus is characterized by Coker, the 

 oosphere is typically centric, and in dehiscence of the sporangium 

 an apical cap or segment falls away exposing the spores, which 

 then swell and emerge in successive groups. Since this type 

 of dehiscence has not been previously described, and may prove 

 inconstant, the validity of the genus is in question until the 

 species has been more extensively investigated. 



4. Dictyuchus Leitgeb {Bot. Zeitung, 26: 502, 1868). 



This is a small but extremely interesting genus. Four named 

 species, D. magnusii Lindstedt (Humphrey, 1893: 132), D. sterile 

 Coker (1923: 151), D. achlyoides Coker (1927: 218), and D. mono- 

 sporus Leitgeb (Couch, 1924 b: 116) as well as two unnamed 

 species (Fig. 58) studied by Weston (1919: 287) and Coker and 

 Braxton (1926: 144) respectively have been reported from North 

 America. The genus is discussed by Coker (1923), and reference 

 made to a few additional forms known abroad. Except in the 

 doubtful species, D. polysporus Lindstedt the oogonia are mono- 

 sporic. The genus is outstanding from the fact that both 

 heterothalHc (Couch, 1924 b: 116) and homothalhc (Coker and 

 Braxton, 1926: 144) strains have been demonstrated to exist. 

 The work of Couch on heterothalhsm is being continued and may 

 be expected to result in a better understanding of forms known 

 thus far only in the sporangial condition. In other genera of 

 the family heterothalhsm is as yet unknown except in a single 

 species of Achlya (Coker, 1927: 207). 



The genus Dictijuchus is characterized chiefly by the behavior 

 of the sporangiospores which after encysting in the sporangium, 

 escape from the cysts through individual pores in the sporangial 

 wall and swim away as reniforni laterally biciliate zoospores. 



