DISEASES OF THE SKIN. 265 



plant that bears them, and also greatly inclined to turn 

 led. The acid they contain is partly acetous, but more 

 of the astringent kind. 



The diseases of the skin, to vvhich many vegetables 

 are subject, are less easily understood than the forego- 

 ing. Besides one kind of Honey-dew, already men- 

 tioned, p. 144, something like leprosy may be ob- 

 served in Tragopogon inajor, Jacq. Aust7\ t. 29, 

 which, as I have been informed by an accurate ob- 

 server, does not injure the seed, nor infect the progeny. 

 The stem of Shepherd's Purse, E?2gL Bof. t. 1485, is 

 occasionally swelled, and a white creani-like crusty 

 afterwards powdery, ensues. The Vvliite Garden 

 Hose, Rosa alba, produces, in like n^anner, an orange- 

 coloured powder. It proves very difiicult, in many 

 cases, to judge whether sucli appeai'ances proceed from 

 a primary disease in the plant, arising from unseason- 

 able cold or wet, or are owing to the baneful stimulus 

 of parasitical /7^;?^'7' irritating the vital principle, like 

 the young progeny of insects as above related. Sir 

 Joseph Banks has, \vith great care and sagacity, traced 

 the progress of the Bliglit in Corn, Vredo frumcnti, 

 Soiccrb. Fung, i. 140, and given a complete history 

 of the minute fungus which causes tliat appearance. 

 See Annals of Botanij, r. 2. 51, t. 3, 4. Under the 

 inspection of this eminent promoter of science, Mr. 

 Francis Bauer has made microscopical drawings of 

 many similar fungi infecting tlie herbage and seeds of 

 several plants, but has decided tliat the black swelling 



