FUNGOID PESTS OF FOREST TREES. 



365 



White Boot-Rot. 



Dematophora necatrix. 



Bosellinia necatrix (Pr. & Del.), PI. XIV. fig. 20. 



This scourge has also been called Dematophora necatrix (Hart.), and 

 has occurred in its earlier stages in this country. It attacks Vines, Fruit 

 Trees, Maples, Oaks, Beeches, and Conifers. 



The mycelium spreads rapidly underground, attacking the rootlets of 

 almost any plant with which it comes into contact, ultimately killing 

 them. In trees the mycelium travelling upwards bursts through the 

 bark as a fluffy snow-white mass. Minute sclerotia are formed in the 

 diseased rootlets, which produce conidia upon dark-coloured hyphse. The 

 mycelium, at first white, at length becomes brownish, and produces pear- 

 shaped swellings, which are reproductive. 



The highest form of reproduction is rarely developed, and consists of 

 large black perithecia, surrounded by bristly conidiophores, and enclosing 

 asci containing eight dark brown sporidia. 



The soil should be well drained, affected plants isolated by trenching 

 around the roots. Dead trees and roots should be removed as soon and 

 as completely as possible, as all the fragments of mycelium are liable to 

 disseminate the disease. 



Hart. & Som. Vis. Trees, p. 82 ; Mass. PL Dis. p. 120, f. 21. 



Plane-Leaf Nerve Anthracnose. 

 Glceosporium nervisequum (Fckl.), PI. XIX. fig. 9. 



A common anthracnose on Plane leaves, forming irregular bleached 

 spots on either side of the midrib and principal veins of the leaves. The 

 pustules are scattered over these spots, on the under surface, and are 

 round or oblong, brownish and at length black, splitting longitudinally or 

 irregularly. The conidia are oblong or pear-shaped (12-15 x 4-6 /i), 

 hyaline, seated upon long, colourless, and slender footstalks (20-25 ^ long). 



This species reaches its full development, as far as at present known, 

 whilst the leaves are still attached to the tree. Wherever it is possible 

 to reach and remove the diseased leaves they should be collected and 

 burnt. 



Recorded also in France, Germany, and Italy. 



Grevillea, xiv. p. 124, No. 616 ; Sacc. Syll. iii. 3716 ; Mass. PL Dis. 

 284, fig. 76 ; Hart. & Som. Dis. Trees, p. 140. 



Plane-Leaf Anthracnose. 



Glceosporium platani (Mont.). 



This second species of anthracnose occurs also on living leaves of 

 Plane trees, but does not form spots along the midrib and nerves, but the 

 minute pustules are scattered over discoloured portions of the leaves, 

 which may be marginal or otherwise. The conidia have a tendency to 

 become fusiform or sometimes oblong (14-15 x 5-6 /*) with many small 

 nuclei. The pedicels are short and slender (not exceeding 5-6 ^). 



