INTRODUCTION TO ORYPTOGAMIC BOTANST. 



275 



280. One great peculiarity iu the genus Erysiphe, or the 

 genera more immediately allied to it, consists in the variously 

 shaped processes which at length radiate from the perithecia, 

 and are at the same time altogether independent of the myce- 

 liirni. few objects are more beautiful under a microscope of 

 moderate powers (Fig. 64). The mycelium in these species is 

 often pure white, but is sometimes tinged in parts with brown, 

 and occasionally assumes a imiform brown tint, paving the way 

 for Meliola. No species of Erysiphe is found, as far as I am 

 aware, in very warm climates. They were at one time sup- 

 posed to be rare in the United States,* but this is far from 



Fig. 63. 



a. Perithecia of Capnodium Thwaitesii, Berk., and a portion of ostio- 

 lum. Both magnified. Sent from Ceylon, on the capsules, as it appears, 

 of some Ardisiad. 



b. Capnodium Citri, producing young and mature perithecia, with a, 

 portion yielding the fruit of an Antennaria. Magnified. From speci- 

 mens on imported lemons, and on leaves from Dr. Lfeveill6. 



c. Fertile thread of Antennaria Bobinsonii, Berk, and Mont. From 

 an authentic specimen. 



* The vine mildew does not occur in the United States on native 

 vines, but only on those which are imported ; and the American varieties 

 cultivated in Switzerland and elsewhere, as the Isabella, Catawba, 

 and York Madeira, are uniformly exempt. 

 18* 



