GUMMOS1S OF PRUNUS JAPONICA 307 



in the bark, broken branchlets, and more especially at those 

 points where leaf-buds or flower-buds have been broken 

 off by birds. An olive patch of Cladosporium first appears 

 at the diseased point, and after the conidia are dispersed the 

 drop of gum appears, and into this gum the hyphae of the 

 fungus extend, keeping pace with its increase in size, but 

 not projecting beyond the surface of the gum-mass. The 

 hyphae at first are colourless and very slender, but as the 

 mass increases in size the tips of the hyphae nearest the 

 circumference become tinged olive, and broken up into 

 short, irregularly shaped chains of cells. When the mass 

 has reached its full size, the peripheral portion is densely 

 crowded with the coloured chains of cells, many of which 

 produce dense masses of cells or micro-sclerotia with thick, 

 dark-brown walls. When this stage of development has 

 been reached, if the mass remains damp and distended, 

 the large brown cells and micro-sclerotia give origin to 

 myriads of very minute hyaline conidia which are con- 

 tained in the dense gum-mass, and have been produced 

 in the absence of oxygen, or in an anaerobic manner. If 

 conditions remain unchanged, the minute conidia, when 

 liberated from the mother-cell, increase at a rapid rate by 

 germination, or in a yeastlike manner, until finally the 

 originally black surface of the mass becomes white and 

 opalescent. Eventually the mass is washed to the ground 

 by rain, and there the conidia continue to reproduce 

 themselves by gemmation. 



After a gum-mass has been removed, a large cankered 

 wound, sometimes extending to the pith, is revealed. 



On the other hand, if the black masses are washed to 

 the ground by rain, and dissolved before the commence- 

 ment of the production of conidia, the large brown cells and 



