558 
their neighbourhood. Amongst plants exhibiting this are trees 
like the mulberry, olive, vine, fig, and vegetables like potatoes, 
turnips, beetroot, and many others. As yet, however, investiga- 
tions giving satisfactory explanations of their occurrence are in- 
conclusive. It is, however probable (says Tubeuf) that they are 
primarily due to errors in cultivation, while the bacteria which are 
always found associated with them are of secondary importance 
as disease-producers. 
Gumosis or Sour Sap, which are results rather than causes, 
may probably be traced to an abnormal condition of the soil. Sour 
Sap when the roots die first, may be due to too much water ; and 
when the tops die first, to the sudden lowering of the temperature. 
A checked sap circulation from the stock to the scion may also 
bring about the trouble. Improperly fed trees, or trees supplied 
with indigestible (unassimilable) food, are less apt to withstand 
the attack, and succumb. 
The trouble shows in a variety of ways. The young spring 
shoots suddenly collapse and wither. In that case, cut hard back 
before the poisonous sap can travel back to the healthy parts. In 
other instances, the foliage and twigs seem all right, but the fruits, 
when the size of a wallnut, stop growing, turn brown, and show a 
gummy exudation on dark-coloured patches. A microscopic ex- 
amination discloses the presence of numerous fungi, often of the 
Macrosporium tribe. A liberal dressing of 5lbs. to 10lbs. of super- 
phosphate of lime in the win'er, with lime added. often saves trees 
predisposed to gumming. McAlpine attributes the cause in some 
instances to a fungus: Clasterosporium carpophilum. Bordeaux 
mixture has been found an efficacious treatment when applied in 
the autumn or early winter, even before pruning ; every bud must 
be soaked. 
A somewhat similar disease, supposed, however, to be of bac- 
terial origin, at times attacks young apricot trees, when two to 
four years old. It is recognised by the leaves or part of the tree 
turning yellow and falling off. The limbs from which the leaves 
fall, when cut through, show a black heart. 
Prune these limbs back as far as they show the black heart, 
and also shorten the limbs that are not diseased. Disinfect the 
knife after it has come into contact with the diseased sap. (See 
above.) 
Lear Rust (Uromyces Amygdale, Cook, and Puccinia pruni 
spinose, Pers.).—Very prevalent in demp Iccalities (late in the 
summer) on peach trees, and also the almcnd, nectazine, spricct, 
and plum. 
The leaves are picked with yellow spots on the vpper svrfece 
of the leaf ; these yellow spots are often surrovnded with a purplish 
ring, and they have on the other side of the leaf brown spots of 
fungoid growth. The leaf tissue attacked by these spots becomes 
