14 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



When first discovered this fungus was called Oidium bidlatum, until 

 the presence of asci was determined. 



M In many cases these blisters formed two parallel lines on either 

 side of the midrib, but sometimes they were irregularly scattered over 

 the leaf. In some cases the blistered part had become black, and in 

 others the portion of the leaf which had protruded had fallen out, so as to 

 leave a regularly defined aperture. The cavities were found to be lined 

 with a thin white stratum, consisting of myriads of confluent white 

 specks of a waxy rather than a powdery appearance." 



It is incumbent upon the cultivator to pick oft' all the blistered leaves 

 and burn them, so as to keep a check on reproduction. Spraying young 

 trees with Bordeaux mixture at intervals of a fortnight may be pre- 

 ventive. 



Joiirn. B.H.S. ix. p. 48 ; Sacc. %//. viii. 3343 ; Mass. PL Dis. 90, 

 fig. 13 ; Cooke Hdbk. No. 2232, fig. 342. 



Peak-leaf Blight. 

 Entomosporium maculatum (Lev.), PI. X. fig. 10. 



This disease is very destructive in the nurseries of the United States, 

 although its presence in this country is rather doubtful. 



Small red spots on the leaves first appear : these increase in size and 

 become brown, or it may extend over the leaf, which then shrivels and 

 falls to the ground. 



The conidia, or sporules, have a very peculiar form, consisting of two 

 nearly equal uncoloured cells attached end to end, and two smaller cells 

 on opposite sides at the point of attachment, so as to present an unequal 

 cross-shaped body. These conidia are produced superficially, in consider- 

 able numbers upon the leaves, extending also to the fruit (18-20 x 12 ll). 



It also attacks the leaves of the Quince. Pear fruits when attacked 

 are liable to crack ; hence a common name for the disease is "cracker." 



Spraying with Bordeaux mixture holds the disease in check, using a 

 V&py dilute solution. Dead leaves should be collected and burnt. 



Sacc. Syll. iii. 3501 ; Mass. PL Dis. 276, fig. 73 ; Galloway, Rep. 

 Ag\ :. U.S.A. 1889, p. 357, pis. viii. ix. ; Tubeiif, Dis. 480. 



Pear-leaf spots, as distinct from those on Apple, are also recorded as 

 Phyllosticta pvrina and PJu/llosticta piricola in Southern Europe, Asco- 

 chyta piricola in Italy, and Scptoria n'ujcrrima in Germany. 



Pear Scab. 

 Fusicladitm pvriwum (Lib.), PL X. fig. 11. 



lietweon the Pear scab and the Apple scab there seems to be very 

 little diU'cnnee except in name. The conidia are the same in size, and 

 the little dim -roiicr in form can scarce; bo material. 



Tlx external m ap 1 f efltatlODB) both on the leaves and the fruit, are very 

 imilar: in the former case both form irregular velvety olive patches, 

 which are apt to have a dendritic appearance on Apple leaves. 



