820 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



There is very little indication on the upper surface of the leaves, but 

 the under surface is either sprinkled or closely beset with the roundish 

 pustules, both of the uredospores and teleutospores, usually in company, 

 the latter darker than the former, but both of them equally powdery. 

 The cluster cups are rare. 



The uredospores are one-celled, roundish, and of a cinnamon brown, 

 the surface studded with minute spores (17-28 x 14-19 /u). 



The teleutospores are nearly black in the mass, oval, divided across 

 the middle into two cells, with a slight constriction at the suture. The 

 apex of the upper cell is furnished with a small papillary tubercle ; the 

 lower cell is attached to a deciduous stem. The whole surface of the 

 spore is covered with small warts (26-35 x 19-23 fx). 



Possibly should a patch of Mint become diseased, it would be well to 

 try cutting it down to the ground and burn it, since it may prove that 

 the disease has not extended to the roots, and the new growths may be 

 free, especially if cut down before the teleutospores have matured and 

 fallen to the ground. 



Common nearly throughout Europe, and in South Africa and North 

 America. 



Sacc. Syll. vii. 2180 ; Mass. PI. Dis. 240 ; Cooke, M. F. p. 204, 

 figs. 69, 70 ; Cooke, Hdbk. No. 1474 ; Pkncr. Br. Ured. 157. 



Rhubarb Cluster Cups. 

 JEcidium rubellum (DC). 



Rhubarb leaves in gardens are sometimes disfigured by the large 

 patches of this parasite, although by no means commonly so. The same 

 fungus is common on the leaves of various species of Dock, from which 

 it may extend to Rhubarb. 



It is very handsome, as far as appearance goes, and forms large crim- 

 son spots, nearly an inch in circumference, while in the centre of these 

 spots the cluster cups are crowded and densely packed together. The 

 white edges of the cup are torn like a fringe, and the aBcidiospores, which 

 occupy the centre of the cup, are produced in chains in the interior, and 

 are nearly globose and rough. 



No further development has been seen upon the rhubarb leaves, 

 since it is affirmed that both the Credo and Puccinia are developed upon 

 another and quite a different species of plant, which in reality is one of 

 the Grasses. But our disease now concerns only the rhubarb leaves. 



Sacc. Syll. vii. 2204 ; Cooke, M. F. 194 ; Cooke, Hdbk. No. 1632. 



Diseases of Beetroot will be better treated in connection with Field 

 Crops. 



Spinach Black Mould. 



Heterosporium variabile (Cooke), PI. VIII. fig. 124. 



The fading leaves of Spinach are liable to be invaded by a species of 

 black mould, similar to that which affects Carnations, which is by no 

 means so harmless as black moulds often are. The threads of the 



