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 (Erysiphe Cichoracearum, or 

 Oidium erysiphoides var. Cucurbitaruni) is a serious en- 

 emy to cucumber culture if it once gains a good foot- 

 hold. It will soon ruin the plants. The disease i.j 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 



