249 



and they were particularly abundant in tlie scattered vessels or 

 •tracheids which contained no brown material. In the medullary 

 rays the " browning " of the cells was very irregular, some of 









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Text jig. 3. — Hyphae of Sterei>m in the wood vessels of apple, 



"Bramley's Seedling." 



the cells containing hyphae having brown walls and contents, 

 while others, which contained hyphae, were otherwise unaltered. 



(5) Spiraea japonica var. glabrata (sp. glabrata). — In 



October, 1918, I observed one silvered shoot of the current year's 

 growth in one plant amongst 33 others growing at the Royal 

 Botanic Gardens, Kew. This Spiraea belongs to the section 

 which is pruned to about 4 to 6 inches above the ground. The 

 first two buds lying below the point of pruning were dead, and 

 the silvered shoot had developed from the next bud at a point 

 about 5 cm. below the cut surface. On splitting the branch 

 which bore the silvered shoot, slight discoloration of the wood 

 could be traced from a point about 3 cm. below the silvered 

 shoot to its point of origin, and then up that shoot to a height 

 of 4 cm. 



The leaves could not be examined microscopically. In the 

 roots and in other parts of the shoot no trace of hyphae was to be 

 seen except in the discoloured tissues. The hyphae were 

 followed downwards for 5 cm. from the point of pruning, and 

 for about 3*5 cm. up the silvered shoot. The discoloration was 

 everywhere more extensive than the distribution of the hyphae; 

 the latter occurred at the periphery of the wood, whence they 

 could be traced inwards, branching in all directions and 



occasionally developing clamp connections (see Text Fig. 4). 



From the above observations, it is evident, in this particular 

 instance, where onlv one shoot out of many on the same bush 

 and amongst other plants in the same bed became silvered, that 

 the fungus had penetrated through a wound caused by pruning. 



(6) Neviusia alabamensis. — During the late summer of 1918, 

 a plant of this species growing at Xew, was noticed to be silvered. 

 It was not examined until November, when a silvered plant was 

 dug up, with its roots, for laboratory investigations. The root 

 stock had suffered injury and was distinctly discoloured; a part 



