14 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Sacc. Sijll. vii. 2192 ; Cooke, M. F. p. 196 ; Plow. Br. Ured. p. 161 ; 

 Cooke, Hclbk. No. 1613. 



Buckthorn Powdery Mildew. 

 Microsphcera divaricata (Wallr.), PI. XVI. fig. 25. 



This mildew makes its appearance on the leaves of Rhamnus Frangula, 

 and very often, as in this country, proceeds no further than the produc- 

 tion of conidia. The mycelium is thin and evanescent, producing the 

 usual erect septate threads, which separate in joints, and constitute the 

 conidia. The receptacles are minute and globose, with a few divergent 

 appendages, about five times as long as the diameter of the receptacles. 

 About four asci are contained within each mature receptacle, each of 

 which encloses four sporidia. 



It is found in France, Germany, Belgium, and Finland. 



Subject, like other epiphytes, to the influence ofjsulphur. 



Sacc. Sijll. i. 37 ; Lev. Ann. Sci. Nat. 1851, xv. t. 8, f. 18.] 



Guelder Rose Leaf-spot. 

 Septoria viburni (West). 



This leaf-spot is to be found both on Viburnum Opulus and Viburnum 

 Lantana. The spots are on the upper surface, and are of irregular form, 

 whitish in the centre and brown at the circumference. The receptacles 

 are minute, like black dots, and the sporules cylindrical, obtuse at the ends 

 with from five to seven guttules. 



Known in Belgium and Italy. 



Sacc. Syll. iii. 2657 ; Cooke, Hdbk. No. 1321 ; Grevillea, xiv. 101. 



Guelder Rose Mealy Mildew. 

 Microsphara Hcdivigii (Lev. f.), PI. XVI. fig. 26. 



The leaves of Viburnum Lantana are subject to the mealy mildew, 

 which covers them with a thin mycelium, giving a frosty appearance for a 

 time, but finally vanishes. The receptacles are minute and globose, as 

 usual, scattered over the mycelium. The appendages which surround 

 the receptacles are few, and a little longer than the diameter of the 

 receptacles. 



The number of asci in each receptacle is limited to four, and each 

 encloses four sporidia. 



This mildew is known in Belgium, Italy, Germany, and North 

 America. 



Sacc. Syll. i. 35 ; Cooke, Hdbk. No. 1918, fig. 316. 



Spindle-tree Rust. 

 Caoma cuonymi (Gmel.), PL XVI. fig. 27. 



This golden rust has been several times found on the leaves of 

 Euonymus europaus, seated upon paler spots ; the pustules are small, and 

 densely aggregated, sometimes disposed in circles, becoming confluent in 



