286 LANDSCAPE GARDENING. 



but a few spores only began the work of destruction. It is 

 during hot, moist weather that they grow most rapidly, and 

 while we may sometimes escape if we do not use fungicides, 

 the wise gardener will be prepared to make the application 

 of the fungicides described on previous pages. 



Among the many fungi injurious to ornamental trees, 

 shrubs, etc., the following are among the most destructive: 



RUSTS. This term has been applied in more or less of 

 an arbitrary manner to a large group of fungi that produce 

 masses of spores on the surface of the leaves, generally 

 yellowish or brownish in color, but when of a white color 

 they are often called the " white rusts " or mildews. The 

 spores germinate on the surface of the leaves, their roots or 

 feeding-parts (called mycelia) penetrate the leaf through 

 the stoma or breathing-pores, and after feeding and develop- 

 ing for greater or less time, according to the species or the 

 condition of the weather, fruit (spores) is produced on 

 stalks or in masses on the surface of the leaf, these spores 

 being scattered by the slightest breath of air. Of the true 

 rusts I shall mention only a few of the most important, with 

 the remedies most effective, but many others of a similar 

 character may be destroyed or prevented from doing harm 

 in the same manner. 



POPLAR-RUST (Melanosporium populina), ROSE-RUST 

 (Phragmidium mucronatum}. HOLLYHOCK-RUST (Puccinia 

 malvacearuDi), LINDEN-RUST (Cercospora microsora). 

 The growth of all of these pests takes place under about the 

 same conditions, i.e., a weakened growth of the tree or 

 plant from any cause and in close, moist, hot weather. 

 Strong-growing, healthy plants are less liable to attack than 

 those of a weak growth, though a too vigorous and soft 

 growth may be produced by too much enrichment of 



