THE FUNGI WHICH CAUSE PLANT DISEASE 



101 



in the West Indies; P. Candida Fcl. on the primrose in Europe 

 and upon non-economic Primulaceae in America; P. maydis Rac."'' 

 the cause of a disease of com in Java. [Its identity with Sclero- 

 spora graminicola is suggested by the recent studies of that species 

 by Butler.] P. vincae Schr. on Vinca minor in Europe; P. myoso- 

 tidis de Bary on several species 



fe3:>< 



Fig. 70.- 



-Mucor: zygospore formation. 

 After Brefeld. 



of forget-me-not and related 

 genera in Europe and America; 

 P. cannabina Otth. on hemp in 

 Europe and Japan; P. con- 

 glomerata Fcl. upon alfilaria 

 in Europe; P. ficariae Tul. on 

 various species of Ranunculus 

 both in the old and the new 

 world; P. antirrhini Schr. on 

 the snapdragon and related 

 hosts in Europe; P. nicotianaB 

 Speg."* on various ornamental 

 species of Nicotiana in South 

 America and California; P. Va- 

 leria mellse Fcl. in Europe on Valerianella; P. Valerianae Trail on 

 Valerian; P. dianthi de Bary on species of Dianthus in Europe; 

 P. coralljB Tranz. on Campanula in Europe; P. jaapiana "^ on 

 rhubarb in Europe; P. phoenixae Tap. on Phoenix "* and an un- 

 determined species on Para rubber. 



Mycelophagus castaneae Man."* is an imperfectly described 

 form which may belong either to the present group or to the 

 Chytridiales. A serious disease of the chestnut in France is 

 charged to it. 



Zygomycetes (p. 66) 



This group of fungi is readily distinguished from the Oomycetes 

 by its isogamous sexual organs, when these are present. In the 

 absence of sexual organs the general type of sporangium is usually 

 sufficient mark of distinction for those who are even but slightly 

 acquainted with the two groups. The mycelium, if young, serves 

 to indicate relationship to the Phycomycetes. Older mycelium is 

 often septate and would lead the unwary into errors of classification. 



