320 GREENHOUSE MANAGEMENT. 



ing has for its distinguishing feature short irregular 

 threads that project from it. 



Like many other diseases, this fungus is seldom 

 troublesome unless there is some inducing weakness in 

 the plants, and an excessive amount of water, an excess of 

 nitrogenous matter in the soil and, particularly, cold 

 drafts of air upon the plants, will hardly fail to induce 

 its appearance. Being entirely superficial in its growth, 

 this mildew is easily kept in check. The fumes of sul- 

 phur are fatal to it, and it is well to always paint the 

 heating pipes with a sulphur wash ; sulphur evaporated 

 by means of an oil stove, or by the heat of the sun, will 

 also be easy to use, as by the last method one has only 

 to apply the sulphur to the plants with a bellows and 

 allow the temperature to run up to 70 degrees before 

 opening the ventilators ; in airing the house after giving 

 this treatment, it should be done gradually, so as to 

 avoid cold drafts. 



rose rust (Phragmidium mucronatum. Winter). 



Although this fungus sometimes attacks tea roses, it 

 is principally troublesome upon hybrid perpetual and 

 other hardy kinds. It first shows as light yellow spots 

 on both sides of the leaves, or upon the stems. The 

 epidermis is soon ruptured and granular pustules are 

 formed. On the leaves these are generally quite small, 

 but as they are very numerous and frequently coalesce, 

 the leaves are often destroyed. When upon the veins, 

 petioles or stems, the spots often extend themselves 

 longitudinally and cover a considerable surface. In 

 that case the stems and leaves become twisted and 

 distorted. 



At first the pustules are of an orange-yellow color, 

 and the spores are spherical or slightly angular in form, 

 and are arranged in chains. Each group is surrounded 

 by elongated bodies called paraphyses, which form a cup- 



