IIHJ Siher-Leaf Disease, III 



were sown under varying conditions (in ordinary soil, in manured soil, 

 in sand, and at different distances apart) during the winter of 1913-14, 

 but none of these seedlings showed characteristic silvering although the 

 foliage of a small number developed a peculiar leaden pallor. Some of 

 the Victoria seeds used in this series were obtained from heavily silvered 

 trees. Large numbers of red currant seedlings (from seed gatheied in 

 1913) grown in boxes also developed normal foliage. 



Other seedlings of various kinds grown under similar conditions by 

 Mr G. 0. Sherrard at the John Innes Horticultural Institution showed 

 dift'erent results. Thus several seedlings of the following varieties of 

 plums, Denniston's Superb, Early Transparent, and Gisborne showed 

 silvered foliage, and nearly all the seedlings of loganberry and "Pheno- 

 menal Berry" possessed silvered foliage. On the other hand seedling 

 apples and nectarines had normal foliage. The seedling Rvbi were 

 planted out in the open and showed a considerable recovery by the 

 autumn. 



These observations show that silver-leaf occurs commonly but ir- 

 regularly in certain seedling plants notably plums, and species of Rubus. 

 In these cases the silvering does not appear to be of pathological signifi- 

 cance as the seedlings grow out of it in time. Nothing is yet known as 

 to the cause of silvering in these seedling plants but our observations 

 indicate that it is not due to a parasitic organism. 



It was pointed out in 1913(2) that plants of the white dead nettle 

 with silvered foliage had been observed, and since then we have seen, 

 during the latter part of the winter and early spring, many kinds of 

 herbaceous plants with silvered foliage including Lamium •purfureum, 

 LitniiiuK ntii iilf.riccnde. Veronica agreaii-^, Raphanus satiinis, Urtka dioica, 

 Planlago major, rhubarb, and Primula sjrp. Mr G. Lamb writing in the 

 Gardener s Chronicle for November 1.5th, 1913, recorded silvering of 

 tomato foliage. 



Several of the above plants have been microscopically examined by 

 us and like the white dead nettle described in 1913 showed the typical 

 characters of silvering. In these herbaceous plants there appears to be 

 no regularity in the distribution of silvered leaves upon an individual 

 jilant, some branches bearing silvered leaves and others normal leaves. 

 Fresh sections of a silvered leaf of Lamium purpvreum showed no 

 noticeable difference as regards the chloroplasts from those of a healthy 

 leaf, although the epidermis was loose and there was the usual tendency 

 of the mesophyll cells to fall asunder. , 



Two other examples of silver-leaf may be noted. Mr F. J. Chittenden 



