74 



THE LOWER FUNGI— PHYCOMYCETES 



these fungi raises at once the question of their relationship. 

 The generic Hmits used here are those adopted by von Minden 

 (1911: 228, 260) and differ considerably from those of older 

 authors. Schroter (1886: 195; 1892: 67, 84), in his treatment of 

 these forms, includes in the genus Diplophysa all species in which 

 the resting spore bears companion cells. He placed the remaining 

 species in Olptdium and Olpidiopsis, including in Olpidium those 

 with uniciliate zoospores and smooth-walled resting spores, and 

 in Olpidiopsis those with biciliate zoospores and spiny resting 

 spores. Fischer (1892: 16) recognized three genera correspond- 

 ing in their limits with those of Schroter, but in his treatment 

 the name Pseudolpidium replaces Olpidiopsis while Olpidiopsis 



Fig. II.' — Olpidium hrassicae (Woronin) Dangoard. (a) Three swarmsporan- 

 gia with long exit tubes. (6) Swarmspores. (c) Roughened thick-walled 

 resting spores. {After Woronin 1878.) 



replaces Diplophysa. This confusing difference in application 

 of generic names makes necessary a critical consideration of all 

 the points involved. 



The classification of von Minden (1911: 227) differs strikingly 

 from older arrangements in the recognition of the new family 

 Woroninaceae. In this family are placed those forms in which 

 the zoospores are biciliate, and in which the thallus is naked in 

 at least its early stages. The genera Pseudolpidium and Olpidiop- 

 sis included in the Woroninaceae, correspond respectively with 

 Olpidium and Pseudolpidiopsis of the Olpidiaceae and differ 

 from them only in the family characters. 



The companion cell present on the resting spore in Olpidiopsis 

 and Pseudolpidiopsis affords a morphological character useful 

 in generic separation irrespective of the question of sexuality 



