JOUENAL 



OF THE 



Royal Horticultural Society. 



Vol. XXIX. 1904. 

 Parts I. and II. 



PESTS OF THE ORNAMENTAL SHRUBBERY. 



By M. C. Cooke, M.A., LL.D., A.L.S., F.R.H.S., V.M.H. 



Notwithstanding the entirely artificial character of such subdivision, it 

 appears to be the most practical method to separate ornamental shrubs 

 into the two groups of evergreen and deciduous, independently; of 

 anomalies which may here and there obtrude themselves. The same 

 parasite very rarely attacks both coriaceous- and tender-leaved plants. 



CORIACEOUS-LEAVED SHRUBS, 

 or Evergreens, are represented by the following. 



Rhododendron Galls. 

 Exobasidium rhododendri (Cram.), PI. XVI. fig. 1. 



The gall-like swellings on the leaves of Rhododendron ferrugincum 

 and B. hirsutum, and possibly of other species, are sufficiently striking 

 not to escape the notice of even a casual observer. They vary in size 

 from that of a pea to that of a marble, and are often found several of 

 them together in a cluster. At first they are of a pale yellowish-green 

 colour, then they acquire a reddish or roseate tint, especially on the sunny 

 side. When fully and properly mature, the surface is covered with a 

 delicate frosty bloom, like the bloom on a plum. It is in this "bloom " 

 that the fungus exhibits itself, for the mycelium is concealed within tbt 

 tissues of the gall. 



The fruiting consists in the development of erect stout spore-bearers, 

 called basidia, which resemble the same organs on the gills of an Agaric 

 The apices of these basidia carry a definite number, usually four, 

 spicules, each of which supports a spore, or basidicspore. These spores 



B 



