21i FUNGOID PESTS OF CULTIVATED PLANTS. 



No remedy is suggested, except picking off and burning as many 

 infested leaves as possible to prevent dispersion. 

 Sacc. Syll. i. 1589; Cooke, Hdbk. No. 2735. 



Melampsora Carpini is recorded as attacking the leaves of Hornbeam. 



Bikch-leaf Spot. 

 Thyllosticta bctulina (Sacc), PL XX. fig. 25. 



Possibly this leaf-spot bears the receptacles of the earliest stage, or 

 spermogonia, of a species of leaf sprneria [Spharella maculiformis) which 

 is not uncommon on the dead leaves of various kinds of forest trees. 

 There are no definite spots, but the receptacles are densely clustered 

 together in large groups, which have the appearance of spots. These are 

 globose, and immersed in the substance of the leaves, and contain minute 

 curved sporules (4-6 xl-l!, /.i), which are ejected when mature. 



Recorded also in France and Italy. 



Sacc. Syll. iii. 170 ; Grevillea, xiv. 72, No. 39S. 



Another leaf-spot on Birch is attributed to Asteroma Belulce, which 

 occurs in Britain, but is not reputed to cause any serious injury. 

 Sacc. Syll. iii. 1241 ; Grevillea, xiv. p. 75, No. 446. 



Birch-leaf Rust. 

 Melampsora betulina (Pers.), PI. XX. fig. 26. 



This rust is common on Birch leaves from May to November. Hitherto 

 all efforts to discover the cluster-cups of this species, presuming them to 

 exist, have been unavailing. 



The pustules of the uredo are small, pale orange, roundish, and rather 

 powdery. The uredospores are ovate or oblong (25-40 x 10-20 ju), finely 

 rough, and orange-yellow. 



The pustules which contain the teleutospores are at first yellow, then 

 they become brown, and ultimately black. The spores are cylindrical, 

 partaking of the typical form of the genus, closely packed side by side, 

 and slightly wedge-shaped (50xl6/«), pale yellow-brown. 



Reported also in France, Belgium, Netherlands, Germany, Finland, 

 Lapland, Austria, Hungary, Switzerland, Italy, and Asiatic Siberia. 



Sacc. Syll. \ii.21is; Plowr. lull. Ured.p.248; Cooke, Hdbk. No. 1659 ; 

 Cooke, M. F. 219, figs. 189, 190 ; Hart. & Som. Dis. Trees, p. 171. 



BlBCH POLYPORE. 



Polyporus betulinus (Fr.). 



Although tliis polypon h;i long been known as a saprophyte on dead 

 Birch trees, it ha only recently been demonstrated that it will attack and 

 destroy living trees, producing ai first ;i brown discoloration and after- 

 winds causing cracks in the decaying wood, which is replete with the 

 white mycelium. 



The complete fungus, when seen attached to the trunk, is-hoof-shaped, 



