69 
large to show the form of the affected disk with its central spore clus¬ 
ters. The fact of special interest here, however, is that the tissue of 
the branch is altered to a considerable distance from the disk of infec¬ 
tion. This is shown by the darkened outer side of the twig. It is the 
under and more protected portion of the branches which becomes most 
thickly infested by the parasite. A branch one foot long and three- 
eighths of an inch in diameter bore twenty points of infection on the 
upper one-third, while 104 such infections were on the lower two-thirds. 
This condition is common, and it bears on the application of sprays for 
prevention. The protection from the heat of the sun on the under sur¬ 
face of limbs gives better conditions for germination and growth and 
probably accounts for the greater number of infections there. 
Transverse sections show that the parasite sometimes kills the 
tissue of the branch as far inward as the cambium zone and xylem bun¬ 
dles. Figure 4 of Plate xi represents such a section magnified 10 diam¬ 
eters. The cortical parenchyma is mostly affected, but at the center of 
the affected spot the parasite has destroyed the phloem and cambium 
tissues, even penetrating slightly into the xylem rays. The fruiting 
bodies of the fungus are indicated at the margin of the section near the 
center of the infested spot. It can not be doubted that twigs infested 
in this manner at hundreds of places are much injured. 
The direct action of G. circumscissa on the nut is of little or no impor¬ 
tance. It can not penetrate the kernel, and it is only found on the 
husk, where the characteristic circular spots occur. 
The leaf of the almond is the most generally attacked and most seriously 
affected portion of the tree. In the young and tender leaf, when viewed 
by transmitted light, the recently infected tissue shows a yellowish st>ot 
varying in size according to the state of advancement. This spot pre¬ 
sents at this time a dark center. By reflected light the center appears 
light and the margin dark. Later the sclerotia or tubercular parts of 
the fungus develop, mostly within the limits of the central area, though 
not confined to this portion, and when the fascicles of conidia have 
arisen from them there is a blackish point within the light center. 
Viewed as an opaque object under a low power these spore clusters are 
of a dark olive-green color. When the conidia have arisen the infected 
tissue often assumes quite a dark color about its margin, which is usu¬ 
ally well defined and nearly circular. Under the action of the parasite 
the affected piece soon dries sufficiently to shrink both in thickness and 
breadth. The shrinkage in breadth causes its rupture from the sur¬ 
rounding and more or less healthy tissue. It soon becomes entirely ex¬ 
cised and falls to the ground. The opening left is bounded by partially 
dead and thickened tissue, and it looks as if made by fine bird shot. 
The entire effect resembles that produced on apricot, prune, almond, 
peach, and other leaves by the Australian u shot-hole” fungus, Phyllos- 
ticta circumscissa , Cooke. It is distinguishable, however, in most cases, 
