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^ (3) Prunus triloba var. flore pleno.— In 1916 localised 



silvering appeared on a few individual plants of this variety 

 which were growing in a bed at Kew; but in the late season oi 

 1918 the disease had spread to many other plants in the same 

 bed, a few of which were completely silvered. In December 

 several silvered branches were cut off and examined. When 

 removing the bark with a pocket-knife the peculiar discoloured 

 streaks were noticeable again, similar to those mentioned under 

 " Victoria Plum." In the case of one three-year-old branch 

 these discoloured streaks were followed upwards into the terminal 

 bud of the current year's growth. A very characteristic feature 

 in the silvered branches of Prunus triloba is that the bark can be 

 stripped off with comparative ease. On two shrubs Stereum 

 purpureum fructifications were developing. 



Owing to the season being so far advanced, no leaves could be 

 examined. When cutting hand sections of the diseased 9 tern, 

 the same difficulty in obtaining intact slices was experienced as 

 with silvered leaves of " Victoria Plum." Abnormal air spaces 

 occurred in the bast of affected twigs. The cambial cells ami 

 the cells of the adhering tissues fell apart from the xylem. 

 Isolated, single phloem-parenchyma cells were found floating 

 free on the slide ; thus the separation of these cells resembles, 

 the separation of the mesophyll cells of the leaves, resulting 

 apparently from the same cause, namely, the dissolution of the 

 middle lamella. In the three-year-old branch mentioned above, 

 the hyphae were traced to within a centimetre of the terminal 

 bud. Text Fig 2 indicates hyphae in the xylem vessel. 



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Text fig. 2. — Longitudinal section of Prunus trilola tut. flore pleno, 

 showing hyphae in the xylem vessels bordering the cambium. 



The severe pruning to which this variety of Primus is annually 

 subjected immediately after flowering undoubtedly increases the 

 opportunities for the entrance of the fungus. 



(4) Apple Trees. — In October, 1918, Messrs. "White & Sons, 



Paddock Wood, Kent, forwarded to me twigs and leaves of 

 " Grenadier" and " Lord Grosvenor " apple trees which were 

 attacked with Silver leaf. It was practically impossible' to cut 

 entire hand section- of the leaves of " Lord Grosvenor "without the 

 tissue falling apart, owing to the fact that they exhibited a 

 phenon- non similar to that of the leaves of plum>. The 





