110 FUNGOID PESTS OF CULTIVATED PLANTS. 



APPLE-LEAF SPOT. 

 Septoria pyricola (Desm.), PI. X. fig. 1. 



Spotted leaves are common enough in the orchard and elsewhere, 

 but they may have many causes, known and unknown, and cannot all be 

 attributed either to insects or fungi. In most cases the spots on the 

 leaves, although destructive to the leaf, unless very prevalent do not 

 affect materially the general condition of the tree or the production of 

 fruit, except in a few instances of a virulent kind. 



In the present instance the spots occur on the upper surface of the 

 leaves of Apple or Pear, and are of a greyish- white with a narrow brown 

 margin. They are commonly somewhat rounded, from a quarter of an 

 inch in diameter. The substance within the spot is killed by the 

 mycelium and bleached, with the surface sprinkled or dotted with little 

 black points not larger than the prick of a pin. Each of these points 

 consists of a small nearly globose receptacle with a minute pore at the 

 apex which encloses the fruit, or spores, of the fungus. When fully 

 mature these minute sporules ooze out at the orifice in the form of a 

 tendril and spread over the surface of the leaf. 



The sporules in the present species are elongated and threadlike, with 

 about two transverse divisions (60 x 3J /*) of a very pale olive tint. 



Found generally throughout Europe. 



Sacc. Syll. iii. 2624 ; Cooke Hdbk. No. 1320 ; Seem. Journ. iv. f. 27. 



A large leaf-spot (Phyllosticta Pyrorum) is known in the United 

 States, with much smaller sporules (10 x 2 /*). 



APPLE-LEAF BLACK MOULD. 



Coniothecium Qiiestieri (Desm.). 



This mould was first discovered in France nearly half a century ago 

 on leaves of Cornus, and appeared in 1902 on fading leaves of 

 Apple, although we have grave doubts of its being any other than a 

 saprophyte. It occurs on the under surface of completely dead spots of 

 the leaves, or on thoroughly dead and brittle leaves. The tufts are 

 small and scattered in little black dots over the dead parts, but do not 

 occur upon the merely discoloured and fading leaves. 



The conidia are conglomerated in variously shaped clusters of from 

 two to eight cells (about 10 n diam.), of a pale brownish colour, mixed 

 with occasional slender threads. 



Sacc. Syll. iv. 2442 ; Trans. Br. Nyc. Soc. (1903), p. 15. 



APPLE-TREE WHITE MOULD. 

 Oidium farinosum (Cooke), PI. X. fig. 2. 



This mould was first observed in 1870 and 1871 covering the young 

 twigs and leaves of Apple trees with a mealy coating of white mould, so 

 that they looked as if dusted with flour or powdered chalk. Since the 

 above it has become sufficiently common. Although it is a true epiphyte, 

 it is capable of inflicting injury, causing the young leaves to curl, 

 checking their growth, and distorting the tender twigs. 



