S. p. Wiltshire 343 



immediately a subcuticular mycelium, it showed a great tendency to 

 grow out horizontally into the cuticle (Fig. 21), which on the older 

 leaves is of sufficient thickness to allow this. There seems some pre- 

 ference of the fungus for the outer portion of the cuticle, rather than 

 that adjacent to the epidermis, but finger-like processes, especially from 

 the underside, are given off as branches from the main hyphae. Some- 

 times these processes reach the epidermal cell-wall and the formation 

 of a subcuticular mycelium takes place : but it was never observed to 

 reach any advanced stage in development, always remaining very 

 simple (Fig. 22). After a varying interval of time the cells of the fungus 

 die off, their contents becoming converted into dark brownish spherical 

 granules. From very many inoculations on mature leaves, both in 

 bell jars and on the trees in plantations, no conidia have ever been 

 produced. Even when the mature leaves of a resistant variety are 

 inoculated, the same course of events is followed. Fig. 20 shows the 

 dead hyphae of V. pirina in the cuticle of the Catillac pear, a resistant 

 variety which was very heavily inoculated with pure mycelium. It 

 will be noticed also that the epidermal cells show the beginnings of the 

 formation of a phellogen, which in the normal progress of the disease 

 is developed after the attack has developed for some time, and which 

 has been reported by Voges. 



In the inoculation of the mature fruit much the same thing happens, 

 although the cuticle here being much thicker it is much easier to 

 follow what takes place. The infection hypha from the appressorium 

 grows directly into the cuticle (Figs. 11, 12 and 13) and then at its 

 innermost end swells shghtly until it becomes almost spherical (Fig. 14). 

 Growth can now proceed in all directions, but much more easily in 

 a plane parallel with the surface of the fruit (Fig. 15). Occasionally, 

 however, it penetrates slowly, following its original course (Figs. 16 

 and 17). The cuticle is apparently laid down in layers, for with all 

 kinds of stains the innermost layers almost invariably take on a deeper 

 colour than the outer ones, and distinct striations can nearly always 

 be seen, especially where it covers the juncture of neighbouring cells 

 of the epidermis. The direction of growth of the hyphae now seems 

 to follow these striations sometimes to an astonishing length, suggesting 

 perhaps that the physical character of the cuticle is an important 

 factor (Figs. 18 and 19). It has been found extremely difficult to 

 infect successfully the mature fruit (using the term "infect" as explained 

 above) ; and although this is reported to occur under certain conditions 

 the ordinary course of events seems to be for the fungus to die off in 



