INSECTS. 215 



found on thousands of other varieties of the vegetable 

 kingdom, whenever a lessened vitality takes place. Cor- 

 roborative of this view, I had a lot of about 500 plants 

 of Heliotrope growing in 2-inch pots in one of our green- 

 houses last fall, one-half of which were, in September, 

 shifted into 3-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 to-day, December 1st, the 

 " black rust " shows itself on nearly every plant, and the 

 microscope shows on every affected leaf hundreds of 

 these insects, feeding like sheep on a pasture field, while 

 on the shifted plants none whatever can be found. This 

 is only one of hundreds of cases which yearly come un- 

 der our observation, to prove that, from whatever cause the 

 vital action of a plant is impaired, it is placed in the con- 

 dition which in a greater or less degree invites the attack 

 of parasitic fungi (mildew) or insects. 



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

 or downy-looking insect, often very troublesome in the 

 hot-house ; it is quickly destroyed by a solution of 1 Ib. 

 of whale oil soap to five gallons of water ; but, as it often 

 attacks plants of the most tender kinds, that are liable to 

 be injured even by this weak mixture, it is not safe for 

 inexperienced hands to use it before experimenting on its 

 strength, and pej-haps the safest method is simply to 

 brush off the insects with a soft brush, made for the 

 purpose. 



Brown and White Scale Insects. These are less in- 

 jurious and less common to plants than any of the pre- 

 ceding, and are generally found in dark or ill-ventilated 

 green-houses, adhering to the stems and under part of the 

 leaves of hard-wooded plants. The best remedy is wash- 

 ing, or brushing them off by hand ; fumigating, and the 



