FUNGOID PESTS OF FOKEST TREES. 



373 



Black Wood Nodules. 

 Daldinia concent rica (De Not.). 



Large black nodules, from the size of a walnut to that of an orange, 

 have been known for a century to occur on dead wood, especially of Ash, 

 and only recently has it been suggested that the fungus producing them 

 is a wound parasite liable to infest with its spores, or conidia, growing 

 and living forest trees, entering through wounds in the bark. We have 

 met with it scores of times, but never on other than thoroughly dead 

 wood, such as gate-posts, rails, rustic seats, &c, and are not yet convinced 

 of its parasitism. The mature fungus is globose, depressed at the base, 

 smooth and shining, and of a jet-black colour. When cut in sections, 

 the interior is grey, rather firm, forming concentric rings. Hence its old 

 name of Hypoxylon concentricum, and its newer one of Daldinia con- 

 centrica. The periphery everywhere consists of closely packed cells, or 

 perithecia, containing the large, oval-shaped, dark brown sporidia in asci 

 (12-15 x7-10^i), which are ejected when mature, and form a dense sooty 

 covering over the entire nodule. 



Very recently M. Molliard has announced the discovery of conidia, 

 suggested and figured by Tulasne, in the form of a white mould, to which 

 he has given the name of Nodulisporium Tidasnci, possibly a form of 

 Botrytis, with conidia 7-8 x4^-5 /j, colourless or slightly grey. 



Tulasne, Fungi Carp. Selec. t. ii. pi. xiii. figs. 14-16 ; Gard. Chron. 

 1861, p. 72 ; Sacc. 8yU. i. 1515 ; Cooke, Hdbk. No. 2384. 



Oak Cankek. 

 Diaporthe taleola (Sacc), PI. XX. fig. 21. 



The disease which is called Oak Canker is said to prevail until trees 

 are forty years old. It is characterised by brown patches of the bark, 

 which are usually of large size, and on different sides of the tree, whereby 

 the bark is killed, and the tree dies. Pustules are formed in the dead 

 bark, and consist of a kind of cushion, cr stroma, imbedded in it, of an 

 almost black colour, in which are cavities or cells, in which are first 

 developed curved or sickle- shaped conidia. Afterwards flask- shaped 

 receptacles are formed, in small groups, within these same pustules, on 

 the same stroma, and the necks of two or three of these receptacles unite, 

 and grow together into a common neck or opening which extends to the 

 surface of the pustule. Within these receptacles asci, or cylindrical sacs, 

 are formed (150 x 14 /<), which each contain eight sporidia which are oblong, 

 divided in the centre into two cells (18-24 x 7-8 ^u). From the median 

 division projects a hyaline spine on each side, and one at each end of the 

 spore. Both conidia and spores are capable of infecting a healthy tree, 

 by entering a wounded spot in the bark. 



The fungus is known in France, Belgium, Germany, Sweden, and 

 Italy. 



It is suggested that young trees thus infected should be felled to save 

 the rest. 



Sacc. Syll. i. 2426; Mass. PL Dis. p. 112; Hart. & Som. Dis. 

 Trees, p. 99, figs. 46-49 ; Cooke, Hdbk. No. 2502. 



