MILDEW AND BRAND. 
185 
constituting tliat genus is its generic name, also commonly 
derived from the Latin or Greek. In this instance, it is Puc - 
cinia, derived from the Greek puka, meaning closely packed, sin- 
gularly applicable to the manner in which the spores are packed 
together in the pustules. The common features, or generic 
distinctions, of this genus, are uniseptate spores borne on a 
distinct peduncle. 
In returning to the species found on Labiate plants, let us 
suppose ourselves to have strolled towards Hampstead Heath, 
and south of the road leading from Hampstead to Highgate, 
near certain conspicuous and well-known arches, built for a 
purpose not yet attained, are two or three muddy ponds nearly 
choked up with vegetation. Some fine autumnal afternoon, 
we must imagine ourselves to have reached the margin of the 
most northern of these ponds, and amidst a thick growth of 
reeds, sedges, and other water-loving plants, to have found 
the water -mint in profusion and luxuriance, with every 
leaf more or less occupied, on its under surface, with the 
yellow spores of a species of rust ( TricJiobasis ) mixed with the 
browner septate spores of the mint brand ( Puccinia Menthce). 
This is common also on the horse-mint and corn-mint ; we 
have found it on the wild basil and wild thyme, and once only 
on marjoram. Having collected as many leaves as we desire, 
and returned to home and the microscope, we proceed to 
examine them in the same manner as we have already exa- 
mined the mildew, and as a result of such proceeding arrive 
at the following conclusions : — The pustules are small and 
round, never elongated as in the corn mildew, and generally 
confined to the under surface of the leaves (fig. 32). The 
spores are sub-globose, slightly constricted, and the two cells 
nearly two hemispheres with their flat surfaces turned towards 
each other (fig. 33). The form delineated in figure 37 is that 
of the sorus of many of the epiphytal brands, the centre being 
occupied by the closely-packed spores, surrounded to a greater 
or less extent by the remains of the ruptured epidermis. 
Although the species of Puccinia (P. glechomatis) found on the 
leaves of the ground-ivy is said to be very common, we sought 
it in vain amongst every cluster of that plant met with during 
last summer and autumn, until, nearly despairing of finding 
it at all, we at last encountered a plot of ground-ivy covering 
the ground to the width of two or three yards and in length 
eight or ten, nearly every plant being attacked by the brand. 
This was in the corner of a pasture, and the only time we found 
infected plants. The fungus, however, may be as common as 
the plant in other localities. The pustules on the leaves are 
larger than those of the mints, and also confined to the 
inferior surface (fig. 36). The spores are elliptic and but 
