192 DISEASES OF THE ROSE. 



These two last are the most common and injurious to roses, as they 

 frequently cover all the leaves. The most effectual mode of prevent- 

 ing their spreading is, to cut off with care and burn all the infected 

 branches, which will sometimes render necessary the destruction of 

 the whole plant. 



PHRAGMIDIUM INCRASSATUM. Linkius. (Puccinia Rosa.) Small, 

 black groups under diseased leaves, and very common. 



XYLOMA ROS^E. Decandolle. Pustules of a blackish gray, and grow- 

 ing on the bark of the plant. 



ERYSIPHE PANNOSA. Linkius. Numerous white filaments, growing 

 on the young shoots, leaves, and branches. It is commonly known to 

 gardeners as the mildew, and is very destructive to the health and 

 growth of the plant. It is a very troublesome enemy to the Rose, and 

 will sometimes put at defiance every application for its destruction. 

 The most effectual is smoking with sulphur, rubbing with dry flour 

 of sulphur, or syringing with sulphur water. The former should only 

 be practised by a skilful hand, as too much sulphur-smoke will some- 

 times entirely kill the plant. 



CYTISPORA LEUCOSPERMA. Fries. Small, round, white points, grow- 

 ing upon diseased branches. 



HYSTERIUM FOLIICOLUM. Fries. Small, black, oval points, with a 

 furrow in the middle ; found on both sides of diseased leaves. 



SPHJDRIA CLYPEATA. Nees. Black, shining tubercles ; found under 

 the epidermis of diseased plants. 



SPH/ERIA SEPINCOLA. Fries. Dull-black tubercles ; found under 

 the epidermis of diseased leaves. 



PHYSICIA CILIARIS. Decandolle. PARHELIA CANDELARIS. Fries. 

 Marks on the wood ofold decaying rose-bushes. 



The insects which infest the Rose are quite numerous, and 

 their attacks are more or less injurious. Those which are found 

 on the plant in the state of perfect insects are comparatively 

 harmless. The most injurious are those whose larvae feed on 

 the leaves and pith of the trunk and limbs, and thus destroy the 

 plant ; while the perfect insect, like the green fly, will simply 

 stop the growth and impair the health of the tree, by fastening 

 upon the green and tender bark of the young shoots, and devour- 

 ing the sap. The history of most of these is very little known. 

 The classification and knowledge of their characteristics are 

 well understood branches of Entomology, but there is a want of 



