RUSTS. 
323 
found on umbelliferous plants, in wliicb the pustules are inva- 
riably developed on the under surface. Under these circum- 
stances, I have called it the Pennywort rust ( Trichobasis 
hydrocotyles) , whilst still doubtful whether it is not the same 
fungus as that described by Montagne, with whose description 
it agrees in everything, except what is implied by the generic 
name. It should not be forgotten, that the work in which 
Montagne first described this species was published when the 
genus TJredo embraced the present genus, which was sepa- 
rated from it by Leveille twelve years later ; and it is possible 
that this species was included in a more recent work by the 
same author, in error and without re-examination, under 
the old name. An examination of authentic specimens of 
Montagne^s plant would settle the point ; but I know of no 
published collection which contains it. The characteristic 
difference between the two genera lies in the presence of a 
peduncle in the early stage of Trichobasis , and its absence 
in all stages of Uredo . Without wandering further into a 
subject which has not the merit of being very popular, let us 
away to some green lane in search of violets, and having 
found them, take a little of the brown dust from one of the 
small pustules on the leaves, upon the point of a penknife. 
Place this, with a drop of water, upon a glass slide, and make 
a record of what we observe. 
The field is covered with the myriad spores of a rust of a 
nearly spherical shape, brownish in colour, and here and there 
one with a short transparent colourless stalk or pedicel. This 
is the violet rust ( Trichobasis Violarum , B.), very common 
all through the summer and autumn, generally on the under 
surface of the leaves of violets, in woods and hedgerows. 
Should it so happen that the spores when placed under the 
microscope are found to be two-celled, it will prove that instead 
of a rust, or Trichobasis , being under examination, a brand, or 
Puccinia , has been found, which is almost equally common, 
and which may, without such a test, be easily mistaken for a 
rust. According to the theory of di-morphism, this is the 
higher form or complete fruit of the same fungus, which in its 
simple-celled state is called Trichobasis Violarum. 
A similar circumstance may befall the student in examining 
the rust of labiate plants ( Trichobasis Labi'itarum , Lev.), 
which occurs on different species of mint, especially the water- 
mint, about the month of August. I have found a few of the 
two-celled spores of the Puccinia imbedded in the pustules of 
this rust almost constantly, whilst the one-celled spores are 
not uncommon in the pustules of what is regarded as the true 
mint brand ( Puccinia Month ce, P.). 
