CONTRIBUTIONS FROM THE WISLEY LABORATORY. 



54.5 



were free from attack. A method of prevention of this disease is thus 

 at once suggested. 



Probably prompt spraying with potassium sulphide (1 oz. to three 

 gallons of water), together with the destruction of the diseased leaves, 

 will be efficient in checking the spread of the disease when once it 

 appears, as it has with the disease on Narcissus previously referred to. 



As this is the first record of the occurrence of the disease in Great 

 Britain, a technical description of the fungus is given. 



Eamularia macrospora. Fresenius in Beitrdge, iii. (1863) 

 p. 88, figs. 



Spots greenish-grey, bordered with purple-brown; fertile 

 hyphee in fascicles issuing through stomata, straight or somewhat 

 curved, with one or two septa, rather narrower than conidia ; 

 conidia cylindrical, obtuse at apex, straight, usually two septate, 

 25-36 fi long, 2.5-3.5 fi wide, very shghtly constricted at the 

 septa. 



On leaves of Campanula persicifolia from Old Golwall, Malvern. 



3. Streak Disease of Sweet Peas. 



During the past four or five years large numbers of sweet peas have 

 succumbed to a rather mysterious disease called, from one of its most 

 constant and prominent symptoms, " streak." The disease is charac- 

 terized by brown streaks along parts of the stem, a yellowish tinge in 

 the foliage, which fails to develop properly, showing a wrinkled appear- 

 ance; the flower buds become yellow and drop off without open- 

 ing, or in less advanced cases open and show brownish or yellowish 

 marks on the petals, and a general lack of substance. Partial recovery 

 may occur, but usually the symptoms spread, brown spots appear in the 

 I leaves, and finally the plant collapses and dies. One or more of these 

 symptoms may be lacking, but a constant one, though often overlooked, 

 is afforded by the root. In advanced cases many of the root fibres, 

 and possibly the whole root, may be dead and brown. If examination 

 be made earlier, it will be found that brown dead areas occur in the 

 soptical tissues of parts of the roots, sometimes just at the collar, but 

 very frequently in other parts. This symptom has been present in 

 3very well-marked case of ' ' streak ' ' disease examined to the number 

 3f several hundreds. The disease may attack plants in all stages of 

 growth, but it is perhaps generally most noticeable just when they are 

 coming into flower. 



The disease presents some peculiar features, and even yet there are 

 ,50me points that require elucidation. As usual in cases of plant disease, 

 !':he specimens first sent for examination were far from complete, con- 

 sisting of pieces of stem, or even single leaves showing brown spots. 

 Careful examination of these, as a rule, failed to show any trace of 

 uugus, even as mycelium in the tissues, still less of fruiting bodies 



i VOL, XXXVII. . . N N 



