200 CUCUMBER. 
the cavities decay set in and extended finally to the base 
of the fruit. All the fruits upon one of the mongrel 
plants behaved in this manner. In no case had the fruit 
been injured, nor was the decay visible upon the exterior 
until it had extended well down the fruit. I am unable 
to account for it. 
In most instances, the mongrel vines resembled the 
Medium Green (the staminate parent) more than the 
Sion House. The fruits were generally intermediate, 
although almost every gradation was observed. Some- 
times the fruits would vary widely upon the same plant. 
A number of vines bore beautiful fruits twice longer 
than the Medium Green, nearly cylindrical, with very 
few spines; and we are looking for good results from 
this or some similar cross. 
Enemies. — The most serious enemy with which we 
have had to contend in cucumber forcing is the spotted 
mite, which feeds upon the under surface of the leaves, 
destroying the green tissue. This pest is treated in the 
preceding chapter (page 176). 
A large coal-black aphis or plant-louse (probably 
Aphis rumicis, Linn.), has been a serious pest. It is 
the worst aphis with which I have ever had experience, 
and every effort should be made to prevent its becom- 
ing established upon the plants. It can be destroyed by 
persistent fumigation, but it must be remembered that ~ 
the cucumber cannot endure a very heavy smudge. 
The root-gall (already described on pages 84 and 
85) is often serious in cucumber houses. 
The powdery mildew (Zrysiphe Cichoracearum, or 
Oidium erysiphoides var. Cucurbitarum) is a serious en- 
emy to cucumber culture if it once gains a good foot- 
hold. It will soon ruin the plants. The disease is su- 
perinduced by too close and moist atmosphere and a 
too soft condition of the foliage. It usually begins as 
light green or yellowish ragged spots—a quarter-inch 
or half-inch across—on the leaves, and generally soon 
