Chap. XV. D I S T E M P E R S O F C O R N. 75 



to the blades : for it has been frequently obferved, that the hair of 

 white fpaniels has been full of this powder, after they have run thro' 

 a field attacked with this difeafe. It is likewife known, that if the 

 infefted corn is waihed by a plentiful rain, the fiij} difappears al- 

 maft entirely, and the grain fuffers little from it. Farmers give it 

 the name of riiji, from the colour of the powder ; and it feems to be 

 the fame dillemper which the Roman writers call rubigo. 



This 7-uli is ufually imputed to dry gloomy weather happening 

 whilil the corn grows with the greatefl force. We have many times 

 obferved, that when a hot iun fucceeds fuch dry hazy weather, the 

 corn \vas covered' with rujl in a very few days. 



This diftemper is of very bad confequence ; for the fineft corn 

 is fuddenly brought almoll to nothing, when it is entirely attacked 

 with it. 



If nijl attacks the corn whilil: young, before the ftem begins to 

 rife, the hurt is lefs, provided there comes on a feafon kindly to its 

 farther growth. The plants are only weakened, as if they had been 

 fed or mowed. They flioot out anew, and produce ears. The 

 ftraw is fliort, and the ears are fmall. But if both blades and ftalks 

 become rufty, the farther growth of the plant is ilopt, and the 

 grain gets no more nourifliment i fo that the crop is exceedingly 

 diminiflaed. 



This diilemper is well worthy the attention of every inquirer into 

 nature, who interefls himfelf in the fuccefs of farming. 



The learned Mr. Tillet, diredlor of the mint at Troyes, treats of 

 this diftemper, but only occafionally. He thinks it is caufed by a 

 iharpnefs in the air in dry cloudy weather, which breaks the velVels 

 interwoven with the fubftance of the blades and ftem, and makes 

 them difcharge a thick oily juice, which, drying by degrees, is turn'd 

 into that rufty powder. He has exaniined, with a good microfcope, 

 many plants of corn whofe ftems and blades were covered with ruJl, 

 and faw diftindlly many fmall openings in the membrane covering 

 the plant, where the powder lay. He obferved that the juice, now 

 dried to a powder, ilfued from thefe fmall openings, over which he 

 ilill perceived fome pieces of the membrane, which imperfedly 

 covered the openings. 



This diftemper is called mildew in England. Our air is feldoiu 

 fo dry as to exhale all the moifture of the glutinous exfudations, 

 and thereby convert them into the rufty powder above defcribed. 

 The caufe here afligned, feems n>uch more reafonable than the thick 



L 2 clammy 



