UnC INULA 101 



in the forms where the appendages tend to become shorter they 

 also immediately become wider, more rigid, and less flexuous, and 

 one is finally forced to the conclusion that " U. ainpclopsidis " is 

 but the last member of a chain of closely connected forms. 



The occurrence of U. necator on species of Actviidia — a genus 

 of plants belonging to Ternstroemiaceae, an order in no way related 

 to Vitaceae — is very interesting, not only because the vine mil- 

 dew has hitherto been supposed to be confined to vines, but also 

 for the evidence it gives on the question, mentioned below, of the 

 native country of U. necator. Professor Miyabe sent me numerous 

 specimens (now in the Kew Herb.) of this form from Japan as 

 " Uncinula actinidiae" Miyabe mss., but on examination the speci- 

 mens proved to agree well with certains forms of U. necator from 

 America. • Some of the Japanese specimens have perithecia with 

 few (about 8), short, wide appendages, i-i ^ times the diameter of 

 the perithecium ; others have more numerous, sometimes irreg- 

 ularly crowded appendages, up to 28 in number, flaccid and three 

 times the diameter of the perithecium. These Japanese specimens 

 further strengthen the view that no sharp line can be drawn be- 

 tween the long- and short-appendaged forms of the present plant. 

 Some of the appendages of the Japanese specimens show a dis- 

 tinctly swollen base (Fig. 2>6). The apex of the appendages, when 



mature, is strongly helicoid. 



U. necator, or " Oidiuni Tuckeri " as the conidial stage has long 

 been called in Europe, is well known as the vine mildew, a dis- 

 ease which has caused the most serious injury to cultivated vines 

 in both the Old and the New World. The literature concerning 

 " Oidium Tuckeri," dealing with its systematic position, until quite 

 recently a matter of doubt, its appearance, mode of attack, reme- 

 dies, etc., is so vast that only a few references to the most impor- 

 tant works can be given here. Briefly, the history of this vine 

 mildew is as follows : In 1847 Berkeley (27) wrote in the Gard- 

 eners' Chronicle that " The grapes in the neighborhood of .Margate 

 (England) have for the two last years been attacked by a peculiar 

 mildew of a most destructive character." Berkeley named the 

 fungus Oidinm Tuckeri, but even here hinted of its connection with 

 an Erysiphe, The disease appeared almost immediately in all the 

 vinevards of the Mediterranean region, and by 185 1 it had been 



