84 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



pierces the epidermis of the leaf, and enters the tissues, where it 

 spreads in the interior of the leaf-cells, finally rupturing the 

 epidermis to form its spores on the surface of the leaf. 



The fruit appears in small patches a quarter to half an inch 

 across ; these patches are at first pale green, then yellowish or 

 almost white, and in the case of fleshy leaves, sunk a little below 

 the general surface of the leaf, as if they had been pressed down 

 by the tip of a finger. When examined with a pocket-lens 

 each fruit, of which there are several on each pale patch, is seen 

 to be surrounded by a blackish ring, hence the specific name of 

 the fungus. 



The potassic sulphide solution mentioned above destroys the 

 germinating spores of this fungus, and as the parasite has been 

 observed on several different kinds of orchids, spraying all the 

 plants present in a house where the pest has been observed, is 

 necessary. 



Rose Leaf Mildew {Spliccrothcca pannosa, Lev.). 

 This parasite appears in the spring or early summer as a 



Fio. 2.— Hose Leaf Mildew (Sphctrothcca pcmttosa). 

 Early summer form of the disease (1) A diseased rose leaf ; natural size. (2) Summer 

 fl«>n>. produced in chains; highly magnified. (3) A single summer-spore germinating; 



magnified 100 Wmm, 



white or greyish mildew on the leaves and young shoots of rose 

 trees. When the disease is abundant it also attacks the fruit. 



