a 
626 THE SMALLER FUNGI. 
them only a condition of some other fungus! Thus the 
-genus Uromyces contains several distinct kinds of minute 
fungi, of which, for example, we will select the bean-leaf 
rust (U. appendiculata), which consists of brown dusty 
spots, resulting from clusters of spores not enclosed in any 
pustule, excrescence or peridium. Each of these spores 
will be found to be furnished with a tiny footstalk, and by 
means of which they are attached to the living leaf of the 
bean. The spore itself is unilocular, oboval in shape, ter- 
minated by a rounded point, having two distinct cover- 
ings, the outer of a deep brown color and smooth, the inner 
colorless; these enclose a granular matter surrounding 4 
vacant and rounded spot, and having at the top a minute 
opening. These spores are ripe towards the end of summer, 
and in harvesting the crop, the brown and snuff-like powder 
will readily part from the dead foliage, and from the pods, 
and smut the fingers. Like the seeds of the higher plants 
they await the return of spring, when, if having fallen upon 
humid soil, “the spore emits a curved and obtuse tube, 
which, soon ceasing to elongate itself, gives origin to three 
or four sporidia, of a kidney shape.” If the sporidia should 
fall upon a living bean-plant, the tube “on being emitted 
penetrates the wall of any approximate cellule, swells and 
increases into a cylindrical tube equal in thickness to the 
original sporidia, and therefore four or five times the diam- 
eter of the germ-tube before it entered the cellule. The 
contents of the sporidia and external portion of the tube 
pass into the portion within the cellule, and then these exter- 
nal portions perish, and all evidence of the entry is obliter- 
ated, except a very minute point at which the tube remains 
attached to the inner surface of the wall of the cellule. The 
enclosed tube soon elongates, divides, and becomes branched. 
These branches pass into the spaces of the pulp of the leaf 
and become mycelium, a change which takes place in a few 
hours. . Where the sporidia had fallen on the surface of the 
bean-leaf, little white spots soon appear, and presently little 
