110 PRACTICAL FLORICULTURE. 



na 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 omis- 

 sion 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 be- 

 lief that our unremitting practice of fumigating may be, 

 after all, the true reason of our 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 appear 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 Verbenas 

 are kept in a mixed green-house collection, where Fuch- 

 sias, Pelargoniums, Heliotropes, etc., are grown (usually in 

 night temperature of 55 or 60), the Verbena becomes af- 

 fected by black rust ; showing that its minute enemy is at 

 work sapping its life-current. 



I am glad to state this fact, so that the employers of 

 gardeners may not blame their men for incapacity, and that 

 the amateur attending to his own conservatory may know 

 why his Fuchsias or Bouvardias become brown and starved 

 looking, while his Verbenas luxuriate ; or why, when his 

 Verbenas become diseased, the former are in health and 

 vigor. 



Verbenas, whether grown for sale or for private use, if we 

 would have plants in fine health and vigor in May, should 



