Hetercecism, 



cultural Society of Denmark. Schoeler began the study of 

 the subject in 1807, when, by closely observing the yellow 

 spots on the under side of barberry leaves, he came to the 

 conclusion that they were due to a microscopical fungus. 

 In 1 8 10, he noticed that the barberry bushes were nearly 

 free from this fungus, and that the rye was that year almost 

 free from rust.* " I then thought," he says, " that there 

 might possibly be a close relationship between the rust on 

 the rye and that upon the barberry ; and when, in the fol- 

 lowing year (18 11), I noticed that the rust upon the bar- 

 berry appeared much earlier in the spring than the rust 

 did upon the other plants — grasses and cereals — I thought 

 I had found out the true origin of the rust in rye. Still, 

 however, this question again and again presents itself to 

 my mind, ' Where does the rust on rye come from in those 

 places in which no barberries are to be found } ' In the 

 summer of 181 2 I convinced myself that the barberry 

 bushes are indeed able to communicate the rust to the rye, 

 by means of the wind, even to a considerable distance." 



For several years prior to 18 13 he experimented in his 

 garden by planting different kinds of corn around barberry 

 bushes, and found that rye and oats were especially liable 

 to be destroyed almost every year by the rust, which always 

 appeared first nearest the barberries. 



From 1 81 3 to 18 17 he planted large and small barberry 

 bushes in his rye-field. He found that the larger bushes 

 did not give rise to the rust in rye, when they lost their 

 foliage in the process of transplanting ; but, on the con- 

 trary, the smaller bushes, which did not lose their leaves 

 so readily, did give rise to the rust in the r}'e to a very 

 marked degree. 



One of his experiments he thus describes : " I planted 



* By the word here translated "rust" is evidently meant, not only the 

 Uredo, but also the mildew. 



