FUNGOID PESTS OF FOREST TREES. 



369 



It can only obtain access to a tree through a wound, when the 

 mycelium attacks the heartwood, the trunk soon becomes hollow, 

 although the tree may continue to live for some years. It is by medium 

 of the spores that healthy trees are inoculated, and hence to prevent the 

 diffusion of spores all specimens of the polypore should be at once 

 destroyed. 



Sacc. Syll. vi. 5165 ; Cooke, Hdbk. No. 768; Mass. PL Dis. p. 191, 

 fig. 44 ; Soiu. Fang. t. 345 ; Hussey, i. t. 29, 31 ; Mass. Fun. Fl. i. p. 243. 



Living Ash trees in this country have been attacked and killed by a 

 sphseriaceous fungus, Bosellinia ligniaria (Nitschke). Specimens were 

 exhibited by W. Carruthers at the Linnean Society, December 16, 1897. 



Mass. PL Dis. p. 122 ; Sacc. Syll. i. No. 991 ; Greville, Sc. Crypt. FL 

 pi. 82. 



Small Oak-Leaf Anthracnose. 

 Gl&osporium umbtinellum (B. & Br.), PI. XIX. fig. 16. 



This anthracnose has been found occasionally on Oak leaves in Britain, 

 whilst some persons think it is the same species as one which has 

 occurred in Belgium, France, and Germany, although the conidia are 

 twice as large. 



The spots are irregular and angular, minute, and of a brown colour, 

 upon which are seated the almost inconspicuous pustules, from which the 

 conidia are expelled when mature in pallid irregular tendrils. The 

 conidia themselves are oblong (10-15 ^ long), with two nuclei, and at 

 first seated upon long and sometimes forked pedicels. 



Sacc. Syll. iii. 3731 ; Cooke, Hdbk. No. 1412 ; Berk. & Br. A.N.H. 

 No. 1141, t. 3, f. 5 ; Grevillea, xiv. 124, No. 61. 



There are a host of leaf-spots on Oak leaves, which have been referred 

 to fungi of different genera as the cause, but they do not appear to be of 

 sufficient importance as " pests " to require notice. 



Oak-Leaf White Mould 



Microstroma album (Desm.), PI. XX. fig. 17. 



This is a small white mould which attacks the under surface of Oak 

 leaves, appearing to the naked eye somewhat like hoar frost. The very 

 short threads are developed in tufts, which form confluent patches. The 

 conidia are oblong (5-7 x 3 fx), unequal-sided, containing one or two small 

 guttules ; the basal threads about three or four times as long as the 

 conidia. 



We have observed it mostly upon the leaves of young seedling Oaks, 

 and in coppices. 



Known also in France, Germany, Belgium, Italy, Moravia, and South 

 Africa. 



Sacc. Syll. iv. 17 ; Cooke, Hdbk. No. 1831. 



