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surface of which is covered with minute orange dust, consisting 
of the spores of the fungus. These spores only appear on the 
under surface of the leaf, but the spots are observable also on 
the upper surface. The fungus is truly an endophyte living 
within the tissues of the plant, and expanding outwards. To 
its presence Dr. Thwaites attributes stains which are produced 
on the bark of the young branches, and the pale translucent 
spots which are to be seen on the leaves previous to the out- 
break of the orange-coloured spores. 
From the delicate mycelioid filaments which constitute the 
root-like portion of this parasitic fungus, threads arise in 
bundles which burst through the cuticle and produce at the tips 
of the threads the orange-coloured spores. Each of these spores 
has a somewhat irregular form, ovate, pear-shaped, or more or 
less of a kidney shape, covered externally when mature with 
minute globose warts, principally on the convex side, the shorter 
side being usually smooth (PI. CXXXV. fig. g). When fresh they 
are of a bright yellow or orange colour, but this speedily dis- 
appears in drying. The longest diameter of the spore is from 
•035 to *04 of a millemetre, and that of the warts about *003- 
•004 of a millemetre. We have observed these warts to leave 
the surface of the spores, and float in the medium in which the 
spores were examined as minute free globose bodies (PI. CXXXV. 
fig. h). This was not noticed by Messrs. Berkeley and Broome 
in their examination of spores from Ceylon. Probably it may 
be dependent on the degree of maturity at which they had 
arrived. In the early stage the spores are smooth, and may be 
seen attached to the apices of the simple or branched threads 
on which they are produced (PL CXXXV. fig. /). When mature, 
the attachment is so slight that the least touch is sufficient to 
disengage them, and they appear to lie in little clusters on the 
discoloured spots, ready to be dispersed by the slightest move- 
ment of the leaves. 
The fungus thus described was first determined and named by 
Messrs. Berkeley and Broome in the cc Gardener’s Chronicle,” *" 
shortly after its first appearance in Ceylon, under the name of 
Hemileia vastatrix , and was regarded as a very interesting- 
addition to science, from its forming a link between moulds 
and rusts. 
The mode of germination has not been observed in this 
country. It is scarcely probable that vitality in the spores will 
extend beyond the loss of the yellow colouring of the endochrome. 
In Ceylon, however, Dr. Thwaites reports that it is not difficult 
to induce germination. Mature spores removed from a diseased 
leaf and laid upon charcoal kept continually moist, he says,. 
* “ Gardener’s Chronicle ” for November 6th, 1889. 
