FUNGOID PESTS OF FOREST TREES. 



381 



either rounded or oblong, with a tawny margin. The pustules are found 

 also on both surfaces, and are either scattered or disposed in rings. The 

 epidermis of the leaves above the pustules is often blackened and rough. 

 The conidia are curved (10-15 x 2 yu), seated upon short thread-like 

 pedicels. 



Recorded also in Sweden, France, Germany, Austria, and Italy. 

 Sacc. Syll iii. 3719 ; Grevillea, xiv. p. 124, No. 618. 



Aspen-Leaf Rust. 

 Melampsora tremulce (Tul.), PI. XXI. fig. 34. 



This parasite is common enough on the leaves of Populus tremula 

 from June to November. It has been said that the cluster-cups are to be 

 found on the leaves of Mercurialis perennis, having been known hitherto 

 under the name of Uredo confluens. 



The uredospores are produced in small pustules on the under surface 

 of the leaves, or larger when upon the young twigs. The spores are sub- 

 globose or ovate, rough, and of an orange col >ur (15-20 x 14-16 p). 



The teleutosp jres are also found on the under surface, forming abun- 

 dant flattened, cc mpact pustules, at first reddish-brown, becoming black. 

 The spores are closely compressed together, side by side, and are elongated, 

 attenuated downwards, almost wedge-shaped (45-50 x 10-12 »•). 



Rostrup contends that the cluster-cups of this rust are to be found in 

 the species called Cceoma pinitorquum, which occurs on young Pine 

 seedlings. 



It has been found in France, Germany, Switzerland, Netherlands, 

 Finland, Austria, Bohemia, Italy, and Portugal. 



Sacc. Syll. vii. 2111 ; Plowr. Br. Ured. 240; Cooke, Hdbk.No. 1560; 

 Cooke, M. F. 219 ; Hart. & Som. Dis. Trees, p. 164, fig. 96. 



White Poplar Rust. 

 Melampsora cecidioides (DC), PI. XXI. fig. 35. 



This rust occurs on the leaves of Populus alba, and has evidently been 

 united hitherto with Melampsora populina, from which it is probably 

 distinct. It has been suggested that the cluster-cups are to be found on 

 the leaves of Mercurialis perennis, which Dr. C. B. Plowright thinks that 

 he has demonstrated. 



The uredo occurs in small roundish pustules, surrounded by a white 

 wreath of large crowded paraphyses. Uredospores, spherical or elliptical, 

 with a colourless rough coating, and orange contents (17-24x15-17 /*). 

 Paraphyses clavate (40-60x15-20 jj). 



Teleutospores forming small brown crusts, cylindrical, cohering 

 laterally, and truncate at the apex (50 x 10 fx), of a brown colour. 



Has been recorded for France and Germany. 



Sacc. Syll. vii. 2112; Plowr. Br. Ured. p. 241. 



