276 PRACTICAL FLORICULTURE. 



year, one-half of which were, in September, shifted into 

 three-inch pots, to be reserved for stock plants. They 

 were kept side by side and treated in all respects the 

 same. Those shifted, of course, with increased food, 

 grew vigorously and strong, while the unshifted remained 

 comparatively stunted, and on the following December 

 1st, the "black rust" showed itself on nearly every plant, 

 and the microscope revealed on every affected leaf hun- 

 dreds of these insects, feeding like sheep on a pasture 

 field, while on the shifted plants none whatever were 

 found. This is only one of hundreds of cases which 

 yearly come under our observation, to prove that, from 

 whatever cause the vital action of a plant is impaired, 

 it is placed in the condition which in a greater or less de- 

 gree invites the attack of parasitic fungi (mildew) or in- 

 sects. 



Mealy Bug, as it is familiarly termed, is a white, mealy 

 or downy-looking insect, belonging to the same family, 

 from which the cochineal of commerce is obtained. It 

 is an insect of the tropics, and is troublesome only among 

 hot house plants, or such as are grown at a high temper- 

 ature. Fortunately we have now a complete antidote 

 against the ravages of the Mealy Bug by the use of fir-tree 

 oil, mixed at the rate of one pint to five gallons of water, 

 and syringed over the plants once a week. In fact the 

 use of fir-tree oil, mixed and applied as above, has kept 

 our greenhouses almost free from Mealy Bug and nearly 

 all other insects, since we began using it in 1884. The 

 great point, however, is its steady application, it being 

 applied weekly. The proportions above given we find 

 best for Dracenas, Crotons, etc., but for tender Roses, 

 Verbenas, etc., in delicate growth half a pint to five gal- 

 lons of water is as strong as it can be applied with 

 safety. 



Brown and White Scale Insects. These are less inju- 

 rious and less common to plants than any of the preced- 



