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been, from the extent to which the corn was destroyed by mildew in a semicircle, 
about ten yards in diameter, opposite each bush. The rest of the field was free 
from the disease. As a matter of fact the three barberry bushes, or rather the 
places where they had been, were found by looking for the mildewed places in the 
wheat. It was felt at the time that had any disbeliever in the hetercecism of 
the wheat mildew been present, he would have been then and there convinced by 
the logic of facts. 
LIrf-HISTORY OF THE Founeus. 
Since Persoon gave to the fungus which causes the wheat mildew the name of 
Puccinia graminis, in the year 1797, our knowledge of its life-history has progres- 
sively increased, owing to the researches of Tulasne and De Bary, who have shown, 
first, its connection with rust; then its mode of germination; and, lastly, its 
hetercecismal character. The genus Puccinia is purely a parasitic one. Up to the 
present time some eighty species have been met with in Great Britain. A perfect 
Puccinia has no less than five kinds of reproductive forms, to which the following 
names have been applied, viz. :—Acidium, Spermogonia, Uredo, Puccinia, and Pro- 
mycelium. Since these various forms of fructification constitute a cycle, it matters 
but little which we commence with, for if they be only taken consecutively, we 
shall come round to the one with which we started. Perhaps it will be most con- 
venient to begin with the Uredo. 
First Stace: Rust—or UreEpo Spores (ria. 1). 
Uredo linearis.—The well-known rust of wheat consists, as its names imply, of 
elongated masses of orange spores, which, during the summer months, occur abun- 
dantly upon the living leaves of various grasses and cereals. Itis not confined to 
the leaves, for it frequently is found upon their sheaths, upon the stem, and also 
upon the glumes. Ifa speck of rust be examined through a common lens, it will 
be seen to consist of a mass of golden dust, around which can be seen the torn 
edges of the epidermis. This yellow powder consists of oval spores, measuring 
from 25 to 85 mk. long, by from 15 to 20 mk. wide. They are not uniform in 
shape, some being more globose than others, but they are all studded with minute 
protuberances, so as to present a warted appearance. They were originally formed 
beneath the cuticle of the plant, which, as they increased in size and number, they 
ruptured. When mature, these spores readily fall apart, and are scattered and 
carried away by the faintest breath of air. Examined more attentively, the 
majority will be found to possess, at one end, an appendage marking the point of 
their attachment to the leaf from which they sprang. If a young pustule of rust 
be examined in section, it will be found that each spore springs separately from a 
single transparent thread or tube, a portion of the mycelium or spawn of the 
fungus. This mycelium consists of an entanglement of hyaline tubes, ramifying 
between the cells of the plant that bears it; at certain points these accumulate 
together and give off a mass of branches parallel to each other, all pointing towards 
the cuticle of the leaf. These branches become enlarged at their superficial ex- 
tremities, where, eventually, each one produces a single spore. These spores are 
at first like the mycelium—colourless, but soon become filled with yellow endo- 
