72 
THE PLANT WORLD. 
forth by an illustration so well known that the situation will be 
readily grasped even by those who have little knowledge of the 
fungi and no interest in the settlement of the difficulty. 
In 1793 Jacquin, an Austrian botanist, described a curious and 
microscopically beautiful fungus, which he found growing in the 
tissues of the barberry leaf, and named it Lycoperdon pociiliforme. 
This fungus produces numerous cup-shaped receptacles about one 
millimeter across, ten to twenty in a place, clustered upon a 
cushion-shaped thickening of the leaf, and filled with round, 
orange-yellow spores in chains. This fungus was shortly after¬ 
ward transferred to the genus Aecidium, and is known in Eng¬ 
lish as the barberry cluster-cup fungus. 
In 1789 Schrank, a Bavarian botanist, described a fungus para¬ 
sitic in the culms and leaves of various grasses and producing 
rust-like streaks of spores a centimeter or more long, which he 
called Lycoperdon lineare. The spores are not inclosed in a re- 
ceptable, but each is borne on a pedicel, from which it easily 
separates, is brownish yellow, oblong in shape, covered with fine 
sharp points, and has four pores placed equi-distant about the 
equator, through which the germinating tubes may pass. This 
fungus was subsequently placed in the genus Uredo, and is 
known in English as the stem rust of grain. 
In 1794 Persoon of Paris described and named Puccinia 
graminis, also parasitic in the culms and leaves of various grasses, 
and forming black or blackish, erumpent masses, one or two milli¬ 
meters broad. The spores of this fungus are many times as large 
as of the others, and have a smooth, resistant, blackish brown 
wall. They stand compactly side by side, each consisting of two 
cells, which may germinate independently. Instead of falling 
away readily, as in the other two cases, they remain where formed, 
and only germinate after a long period of rest, usually over winter. 
In Great Britain this fungus is called mildew, and in America the 
black grain rust. 
Three more diverse forms can scarcely be found among micro¬ 
scopic fungi, and this assignment to independent genera by the 
early mycologists was clearly justifiable. Even in those days, 
however, there were keenly observant persons, who fancied some 
