826 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



at Shrewsbury and almost destroyed by its ravages. A public trial took 

 place in Edinburgh where damage was sustained to a crop through this 

 cause. At other times a limited number of plants have sustained injury 

 in gardens. 



There are declared to be, as usual, three stages in the history of this pest. 

 First, the cluster cups or JEcidixim form, which is by no means trouble- 

 some ; and then the Uredo form, which occurs in small reddish-brown 

 pustules either scattered over the leaves or collected in clusters. The 

 uredospores are either nearly globose or elliptically so, very delicately 

 spinulose (20-33 x 18-27 /j), of a pale orange colour. 



The teleutospores are contained in flattened pustules of a darker 

 colour, and are commonly of two kinds : one form is obovate and without 

 any septa or division (25-36 x 15-23 /u) and the others are club-shaped, 

 and divided into two cells (28-45 x 20-26 n), of a chestnut-brown colour, 

 and externally smooth, with a long slender pedicel. For this reason 

 probably, this species has sometimes been called Puccinia mixta. 



Possibly other rust will sometimes attack cultivated Onions, of which 

 we are said to possess three species. 



This is known, at any rate, in France, Germany, Finland, and Italy. 



Sacc. Syll. vii. 2155, ; Gard. Chron. Oct. 15, 1891 ; Plowr. Br. Ured. 

 148 ; Smith, Field Crops, p. 39. 



Onion Rot Mould. 

 Peronospora Schleideni (Unger), PI. VIII. fig. 134. 



Of all the destructive rot moulds scarce one is more destructive, or its 

 attacks to be more deplored, than the present : which will fall upon a 

 crop of young Onions and destroy them in an incredibly short space of 

 time. 



The mould forms broadly effused patches of greyish-lilac tufts, which 

 sometimes entirely cover the leaves, so that in its early history it was 

 known as Botrytis destructor. 



The fertile threads arise from the mycelium in tufts, and are large 

 and without septa or divisions. The upper portion is branched alter- 

 nately, or in a forked manner, and is again and again divided until the 

 final branchlets are strongly arched. The conidia are obovate or egg- 

 shaped, with the apex obtuse, or a little acute, and of a pale dingy violet 

 (45-55 x 22-25 ,.)• 



The resting spores are produced on the mycelium as usual, and are 

 broadly elliptical or globose, with a comparatively thin and smooth 

 coating. 



This is known in France, Belgium, Germany, Scandinavia, and North 

 America. 



It is recommended as a good plan to sow the Onions in the autumn, 

 so that they are able to make a good growth before the appearance of the 

 mould in the spring. 



Berk. Ann. Nat. Hist. vi. p. 436, t. 13, f. 23 ; Sacc. Syll. vi. 857 ; 

 Cooke, Hdbk. No. 1787 ; Cooke, M. F. fig. 263 ; Mass. B. F. p. 125 ; 

 Berlcse, Icon. xxv. ; Mass. PL Dis. 75 ; Smith, Field Crops, 45. 



