150 PRACTICAL FLORICULTURE. 



above forty-five degrees, and if a temperature can be sus- 

 tained throughout the entire winter months averaging 

 fifty degrees, at night, and not to exceed fifteen degrees 

 higher during the day until the middle of March, there is 

 no doubt whatever of having a healthy ard vigorous stock, 

 providing proper attention has been given to watering 

 and to fumigation by tobacco. 



Continued fumigation is of the utmost importance in 

 the culture of all plants under glass, but it is perfectly 

 indispensable to the welfare of the Verbena. In all our 

 Verbena houses we fumigate, on an average, two or three 

 times each week ; we do not wait to see the aphis or Green- 

 fly, but apply the antidote solely as a preventive. No 

 omission is so inexcusable as that of permitting plants to 

 be injured by this insect. 



Although I have elsewhere stated (see chapter on In- 

 sects) that the very minute one which produces the 

 troublesome "black rust" on the Verbena seems invul- 

 nerable to the fumes of tobacco smoke, yet I have a belief 

 that our unremitting practice of fumigating may be, 

 after all, the true reason of our comparative exemption 

 from its attack ; for although this insect may have the 

 faculty of imbedding itself in the leaf on the approach of 

 danger, its eggs, being stationary and exposed, may be 

 destroyed by the action of the smoke ; at all events, we 

 have repeatedly brought varieties of Verbena severely 

 affected by the rust into our collection, which in a few 

 weeks appeared entirely free from the disease, showing 

 that our treatment, in some way or other, destroyed 

 the enemy. 



There is no question that this insect, so fatal to the 

 health of the Verbena, is most active and destructive in 

 a high temperature ; hence we find that whenever Ver- 

 benas are kept in a mixed greenhouse collection, where 

 Fuchsias, Pelargoniums, Heliotrope, etc., are grown (us- 

 ually in night temperature of fifty-five or sixty degrees), 



