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these trees well enough to distinguish the one from the other, 
will have observed the under surfaces of the leaves of both 
sprinkled with a golden dust, during the summer months, 
and which are the spores of a parasitic fungus. So common 
is this orange-coloured powder on leaves of the trees above- 
named, that we can hardly believe any one to have had a 
branch of either in his hand and not observed it, provided 
any leaves adorned the branch in question. What this para- 
site is, and what its associates, it is our province to endeavour 
to explain. Our figure (Plate XIII. fig. 1) represents a leaf of 
the sallow or goat-willow, with the under surface exhibiting 
yellow patches, consisting of spores, which are magnified in 
the next figure (Plate XIII. fig. 2). This exceedingly common 
rust is termed Lecythea cajorearum , Lev., when in the con- 
dition figured ; but in reality this is only the summer stage, 
bearing the summer fruit of Melamjpsora salicina , which latter 
attains its mature development on the same leaves in the 
succeeding winter or early spring. Of course this latter 
remark applies to the fallen leaves, for at this period all the 
willows and other deciduous trees are bare. But the leaves, 
before they fall, give evidence of the parasite at work ; and if 
the collected decaying mass of rubbish at the base of sallow 
bushes be examined about March, these leaves will be found 
bearing upon them mature heaps of elongated, wedge-shaped 
spores, closely packed side by side, and which, whilst still 
adherent, may often be found in active germination, as repre- 
sented in an allied species at the bottom of our plate (Plate XIII. 
fig. 24). This phenomenon consists in the production of 
cylindrical tubes, more or less elongated, from the upper 
extremity (rarely from the base) of the prismatic spores. 
These tubes are straight or twisted, simple or forked, and 
each of them becomes divided by transverse septa into four 
unequal cells towards their apex, from each of which is pro- 
duced a spicule bearing a sporidium, or spherical secondary 
fruit, in the same manner as in the genera Puccinia and 
Aregma. It should be observed, that the winter spores of 
this rust are borne on the opposite surface of the leaves to 
the summer spores : for whilst the latter are developed from 
the under surface, the former are found on the upper. This 
being also an instance of di-morphism, the summer condition, 
when spherical spores are produced, should not be regarded 
as a distinct plant, and the name of Lecythea ca'prearum does 
not merit retention in the list of fungi. 
There are five species of this interesting group, or genus, 
found in Great Britain, to the residue of which we may only 
briefly allude. It has already been stated that, in summer, 
the yellow spores of a rust are found on the under surface of 
