DISEASE OF TURNIPS. 



01DIUM BALSAMII, Mont. 



By WORTEINGTON G. SMITH, Esq., F.L.8., 



I HE ravages of this fungus have recently taken alarming 

 proportions in Dorsetshire ; it seems, therefore, desir- 

 able that special attention should be directed to it. 



I will briefly give a history of the obnoxious pest as far as my 

 knowledge extends (adverting at the same time to the past and 

 present nature of its attacks upon wild and cultivated plants), 

 and then describe the appearance of the fungus as seen under 

 the microscope. 



Oidium Balsamii is a mildew, or mould, closely allied to the 

 mildew of the vine and the peach, but although it is just now 

 afflicting turnips to an unprecedented extent it is not the "turnip 

 mould " proper. The latter parasite is a close ally of the fungus 

 of the potato disease ; it is named Peronospora parasitica, and 

 as far as my experience goes it is this year unusually common. 

 The two fungi are totally different things, although to the naked 

 eye they are not to bo distinguished from each other. 



Botanists have had Oidium Balsamii in view for more than a 

 quarter of a century. It was first noticed growing on a Mullein 

 Yerbascum montanum in Milan by Balsamo ; this gentleman 

 sent specimens to Dr. Montague under the name of Oidium 

 Tuckeri, he erroneously thinking that it was the same with the 

 fungus of the vine. In 1853 the Rev. M. J. Berkeley recorded 

 the occurrence of the pest on another Mullein Verbascum 

 nigrum in this country. 



