MILDEW AND BRAND. 
187 
Everybody knows the dandelion, but it is not every one who 
has noticed the fungi found upon its leaves. These are most 
commonly of two kinds, or probably the unilocular and bilo- 
cular forms of the same species : the latter we have found in 
the month of May, and the former in August and September. 
The lower leaves of young seedlings have generally rewarded 
us with the best specimens of the septate-fruited brand 
{Puccinia variabilis, Grev.). The pustules occur on both sides 
of the leaf, and are very small and scattered (fig. 39). The 
spores are singularly variable in form : sometimes both divi- 
sions are nearly equal in size ; sometimes the upper, and 
sometimes the lower, division is the smallest; occasionally 
the septum will be absent altogether; and more rarely, the 
spores will contain three cells. From the very variable 
character of the spores (fig. 40) the specific name has been 
derived. 
No species in the entire genus makes so prominent an 
appearance as the one found on the radical leaves of the 
spear thistle ( Garduus lanceolatus) . This latter plant is 
exceedingly abundant, and so is its parasite {Puccinia syn- 
genesiarum , Lk.). From the month of July till the frosts set in 
we may be almost certain of finding specimens in any wood. 
The leaves have a paler roundish spot, from one-twelfth to 
one-fourth of an inch in diameter, on the upper surface, and 
a corresponding dark brown raised spot on the under surface, 
caused by an aggregation of pustules, forming a large com- 
pound pustule, often partly covered with the epidermis. The 
individual pustules are small, but this aggregate mode of 
growth gives the clusters great prominence, and therefore 
they are not easily overlooked (fig. 26). Although not con- 
fined to this species of thistle, we have not yet found this 
Puccinia on any other plant. The spores are elliptical, rather 
elongated, constricted, and without spines (fig. 27). 
Other species of Puccinia are found on Composite plants, 
but with none of these is the present fungus likely to be con- 
founded, if regard be had to its pecular habit. The leaves, for 
instance, of the common knapweed {Centaur ea nigra) are often 
sprinkled with the small pustules of the centaury brand 
{Puccinia composita/rum , Sch.) ; these generally occupy the 
under surface of the lower radical leaves (fig. 30) ; occasionally a 
few of the pustules appear on the upper surface. We have not 
often found this fungus in the neighbourhood of London on the 
leaves of the knapweed, but, on the other hand, we have en- 
countered it very commonly on those of the saw-wort {Serratula 
tinctoria). The spores are oval, scarcely constricted, and not 
attenuated in either direction (fig. 31). Other Composite plants 
than those above named are liable to attacks from this parasite. 
