106 SWEET PEAS 



Mackereth's Sweet Pea manure, which contains this substance, is 

 one of the best fertilisers the grower can stock. 



As a Preventive either gas- lime or the patent destroyers may 

 be used in the winter, but Sweet Peas should not be grown on 

 the same ground again for at least three years. The white worms 

 are so commonly introduced with animal manure that it is a good 

 plan to mix with this equal parts of soot and lime, at the rate of 

 about 2 Ib. to the barrowload of dung. This should be done while 

 the manure is in the heap, well mixing the whole together. 



Diseases of the Sweet Pea. Fortunately for the grower of 

 Sweet Peas the plants have been attacked by few diseases. Whether 

 in a few years, if the present high cultivation continues, some dread 

 disease may appear can only be conjectured. Mycologists tell 

 us that too liberal treatment is responsible for many diseases 

 now prevalent in gardens. Some sensation amongst growers was 

 caused in the spring of 1908 by several writers in The Gardener 

 discussing what they called " Streak Disease." Judging from the 

 flowers staged at the principal shows in the same year only an 



FIG. 11. LEAF-SPOT DISEASE OF SWEET PEAS 



(Peronospora trifoliorum var.) 



K, infested seedling : n, cotyledons in which may have been latent 

 mycelium of fungus ; o, disease spots on radicle, first yellowish then 

 dark brown or black ; p, infected plumule or underground stem ; 

 q, growing point often does not extend but plant collapses, sometimes 

 not appearing above ground. 



L, young plant infected when a few inches high : r, pale yellow spots or 

 blotches on stem and leaves early stage of infection, ultimately 

 brown or black ; s. under side of leaf where spore-bearing condition of 

 fungus produced ; t, stunted growth, the plant seldom advancing to 

 satisfactory flowering. 



M, portion of flowering stem infected by fungus : ?/, pale yellow spots on 

 leaves ; v, brown blotches on under side of leaf on which spore-bearing 

 condition of fungus produced. 



N, seed pod apparently sound externally but fungus growing within the 

 pod and on some of the contained seeds. 



O, seeds from diseased pod (N) : w, perfect seed and normally healthy ; 

 x, seed partially affected by fungus at point of line ; y, seed destroyed 

 by disease and with " stubble " of conidiophores on surface. 



P, cluster of conidiophores bearing conidia or spores of Sweet Pea leaf- 

 spot fungus. 



Q, Oospore or resting spore. 



