RUSTS. 
329 
Tlie under surface of the leaves of the white Dutch clover 
are often sprinkled with black spots, which are nearly round 
and very numerous. These are so many clusters of fungi 
belonging to a different section, in which the threads are the 
important feature. But another parasite is also found on 
leaves of the same plant, in which the pustules are far less 
numerous and regular, and are often found on the petiole as 
well as the leaf, distorting them and twisting them in various 
directions (Plate XII. fig. 31 ) . This is the clover rust ( Uromyces 
opiculata , Lev.), which is a parasite on numerous plants, being 
found also on the great water-dock and other kinds of dock. 
The spores are ovoid and brown, with a short peduncle (fig. 
32). A very beautiful species occurs on the leaves of the 
ladies-mantle (Alchemilla ) , but hitherto I have not been for- 
tunate enough to collect it. 
A very interesting, though small group of allied fungi are 
included botanically under the genus called Polycystis, in 
allusion to the many cells of which the spores are composed. 
In the most recent work on British Fungi, approximating to a 
Flora, viz. “ Berkeley's Outlines," only three species are 
recorded, whilst the most common, at least around London, is 
omitted in error; for it could scarcely have been unknown 
as indigenous to this country. This last is the crowfoot smut 
( Polycystis pompholygodes , Lev.), found on the leaves and 
petioles of the common creeping buttercup (. Ranunculus repens), 
distorting them very much. The leaves and their footstalks 
when attacked, become swollen, as if blistered at first, and 
ultimately burst in an irregular manner, exposing a mass 
of blackish soot-like dust (Plate XIII. fig. 9), which on 
examination will be found to consist of the many-celled spores 
alluded to (fig. 10). Each of these spores appears to have a 
transparent outer membrane, either inclosing an unequal 
number, from two or three to five or six, distinct cells, com- 
pressed together into a spherical form by the outer integument, 
or the interior is divided by septa into as many cells. Each of 
these divisions contains a dark brownish endochrome, or cell- 
contents. As may be anticipated, the spores in all the 
species associated in this genus are interesting objects for the 
microscope. The species on the buttercup may be found 
through the summer and autumn on j Ranunculus repens , espe- 
cially whenever that plant is met with in very damp situations. 
We have seldom found the plant in any profusion without 
its attendant fungus. Another species of these many-celled 
smuts is not uncommon in gardens, on the sweet violet, 
attacking the footstalks of the leaves more commonly than 
the leaves themselves, and swelling and contorting them 
(Plate XIII. fig. 11). In general structure, the spores are very 
