Heterecism. 53 
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 1810, 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 (1811), 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 1812 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 1813 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 1813 to 1817 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 rye 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. 
