WITH NOTES ON OTHER SPECIES. 131 



ThraustotJieca/^ gen. nov. 



Hyphge stout, branching. Zoosporangia fornied from their swollen ends, clavate ; 

 the later ones fornied by sympodial branching. Zoospores encysting within the spo- 

 rangium at once after their formation, somewhat polyhedral from pressure, but with 

 distinct membranes ; soon set free by the breaking up of the very fragile sporangial 

 wall, and then escaping from their cysts to swarm in the laterally biciliate form ; 

 finally encysting again and germinating. Oogonia several spored, with abundant 

 antheridia. 



Thraustoiheca clavata (DeBary). 



Syn.: Bictyuchus clavatus DeBary ('88). 111.: Biisgen, '82, PI. XII, Figs. 1-8. 



DeBary, '88, PI. IX, Fig. 3. 



This, the only species of the genus yet known, strikingly resembles Achlya 

 DeBaryana in its sexual organs, having similar long and branching antheridial threads 

 and smooth oogonia with excentric oospores. But its short, clavate sporangia and 

 the peculiarities in the development of its zoospores separate it widely from the latter. 

 It is known only from near Strassburg, Germany. 



A careful comparison of the characters of this species, as drawn from the accounts 

 of Biisgen ('82) and DeBary ('88), with those of species of Dictyuclius, taken from 

 the American specimens studied by the writer, will furnish, it is believed, suflScient 

 justification for its separation from the latter genus. An account of the diflferences 

 on which the new genus is based will also be found in the discussion of generic rela- 

 tionships on a previous page. The close analogy of the sporangia of this plant with 

 those of Mucor has already been pointed out by Solms-Laubach, to whom we owe 

 the arrangement of incomplete fragments of DeBary's last paper ('83), and he has 

 also hinted at the possibility of generic differences between this and the other 

 described species of Dictyuclius. His suspicions are quite supported by the very differ- 

 ent means adopted, in the two types, for the release of the zoospores after their encyst- 

 ment within the sporangium. The species needs further study, especially with refer- 

 ence to the nature of the intermediate substance said to exist between the zoospores 

 within the sporangium. 



Dictyuchus Leitgeb ('68). 



HyphsB stout or slender, branching. Zoosporangia formed from their swollen 

 ends, usually fusiform ; the later ones formed in basipetal succession below the earlier, 



* dpaoard^, fragile ; ^TJX'^y * case. 



