Sacramento daily record-union., 1888-09-22
CURL LEAF.
Description of It's Cause and Character
istics.

Description of It's Cause and Character
istics.
Many different opinions are held by
cultivators as to the causes of the curl leaf
in peach trees. At recent meeting of a
prominent horticultural society the fol-
lowing were given: Wet weather, dry
weather, cold, hot sun, overflow of sap.
diseased sap, insect, fungus. The follow
ing observed phenomena were also men
toned Trees shed their foliage, some
times only one-half of tree affected, curl
accompanied by cold and wet weather.
badly affected trees produce little fruit.
when the development of the curl is sud-
den trees cast their fruit, limb may be
affected down to q certain distance and
near that healthy growth of leaves may
appear, as diseased leaves drop new and
healthy ones come out, new wood becomes
discolored, outer edge of leaf stops grow
ing, center continues to grow and puffs up,
disease pretty general in 1884 The OBJ
servations are mostly correct and valua-
bic, but it is evident that the conclusion
cannot all be true.
The curl appears early in the spring
and lasts till the middle of summer. The
entire Leaf, or only portion, may be
affected. The diseased portion is pale and
greatly distorted, becoming st ongly con
vex, protruding above, rarely below, or
even IN both directions on the same leaf.
The reformation resembles that produced
on various plants by plant lice. The
structure of the leaf becomes heshy and
thickened; young stems are frequently dis
eased, becoming fieshy in the same way,
and somewhat distorted. A whitish, fine,
velvety appearance often occurs on the
surface Of diseased parts.
Let us examine further to see if we can
find any more minute difference between
the healthy and diseased leaves = any
change in the internal structure to ac-
count for the remarkable change in shape
A cross-Section of healthy leaf, well mag
nihed, shows a row of firm, somewhat reg
ular cells, with their fiat sides to the up
per surface. These form the epidermis,
and their outer wall is thickened to form
the cuticle-the smooth, Shiny surface of
the leaf The epidermis contains no leaf
green. The cells of the next layer are
placed with their ends toward the surface
of the leaf and contain leaf green. When
the disease develops these cells multiply,
first by forming transverse partitions, then
by dividing in all directions till they form
a thick, aeshy layer. The leaf green dis
appears, the epidermal cells also divide, a
more extended space is necessary to con-
tain them, and they find it by forming a
curved surface Other cells of the leaf
partake Of the same compact, feshy
structure
In the case of branches, the green layer
Of the bark is affected, but does not en-
tirely lose its color This excessive activ-
ity in growth is not the kind of change
that is produced by cold or by diseased
sap, but it is known to be produced in
many cases by parasitic fungi. And, in
addition to what has been described, a
fungus is found in every diseased peach
leaf. 1t forms a layer of roundish cells
between the epidermis and the cuticle,
and from this sends out slender, branch
ing tilaments, which form a net work
throughout the diseased part They grow
between the leaf cells, but do not enter
them, and terminate in cluster of short,
root-Gkc branches, which are applied to
the cells and draw nourishment from them.
Some of the threads have been traced into
the leaves from the smaller branches,
where they are believed to live through
the winter, and are found early in the
spring.
When the spores are produced. the lea
becomes little more thickened, fungous
cells from the layer described protrude
through the cuticle, each elongates, then
forms cross-partition near the base, max
ing an oblong, square-topped sack, borne
ON 4 short, thick stalk. These sacks stand
thickly over the leaf surface. They are
the spore cases or asci. AS they are pro-
duced on the outside, the genus is called
Eaooscus, while the appropriate name Of
dgor7nans denotes the species. An ascus
is about one-fve hundredth of an inch
long, much less in thickness and contains
eight roundish spores proportionately
small At maturity the ascus breaks open
at the apex, the spores escape and germi-
nate.
The injury produced consists in destroy.
ing part of the leaf-green in which the
food Of the plant is elaborated, in taking SC
much nutriment for the growth of the
fungus and the abnormal growth of the
leaf, in the final drying up or falling off o.
leaves, and impairing the vitality o
branches. The disease is apt to remair
in tree year after year, ipjuring its croE
and finally killing it.
Relief is to be sought in removing and
burning all diseased portions of branche.
and eli leaves that fall = Country Gentle
man.