PESTS OF ORCHARD AND FRUIT GARDEN. 



13 



and warted on the surface (25-40 x 18-25 m). These spores are produced 

 in chains, readily separating from each other. 



Spots are also to be seen on the opposite side of the leaf to that which 

 bears the Bcestelia and corresponding to it. These are conspicuous by 

 their orange colour, which becomes reddish, sprinkled with blackish dots, 

 which indicate cells containing very minute bodies called spermatid, which 

 are expelled when mature. 



It is recorded in Hooker's "British Flora" that when young Pear 

 trees are planted near old trees suffering from the Bcestelia the young 

 trees have been observed to become much injured by the fungus. Mr. 

 Knight sowed Pear seeds in soil infested with Bcestelia, and the very 

 youngest of the seedlings showed the disease. 



According to theory it is contended that this kind of cluster cups 

 must also have a condition analogous to the Uredo and Puccinia forms. 

 As this is not known to take place upon the Pear tree itself, it is inferred 

 that it must take place upon some other plant. The plant selected as 

 fulfilling the condition is the Savin, and it is contended that the cluster 

 cups of the Pear tree produces those gelatinous exudations on the stems 

 of the Savin which are known under the name of Gymno sporangium. 



(Ersted originated this suggestion in 1865, when he intimated that he 

 had learned that gardeners were of opinion that the Pear fungus was 

 never seen except after the appearance of the fungus on Savin. Hence 

 he set to work to prove by cultures that the Pear fungus would produce 

 the Savin fungus by inoculation, and vice versa. (Fig. 5.) 



Incidentally Stevenson records that the Savin fungus is found in 

 Scotland, but that the other condition, the Pear-leaf fungus, is not a 

 Scottish plant. 



The advice given to gardeners by the theorists is to destroy all Savin 

 bushes, root and branch, if they would save their Pear trees. Berkeley, 

 however, wrote : — " If picking the leaves off carefully and burning them 

 will not do, we may feel secure that an onslaught against the poor Savin 

 bushes will not avail us." 



Known in France, Germany, Switzerland, Austria, and North America. 



Sacc. Sytt. vii. 2608 ; Cooke M. F. 193, t. 2, f. 2021 ; Plowr. Br. Ured, 

 p. 230; Mass. PI. Dis. 257; Thiim. Pom. 73; Cooke Hclbk. No. 1597; 

 Gard. Chron. 1862, p. 689 ; Tubeuf, Dis. 399, fig. 



Pear-leaf Blister. 

 Exoascus bullatus (Tul.), PI. X. fig. 9. 



The blister of Pear leaves is a disease which has long been known in 

 this country, distorting the foliage in a similar manner to the "curl " on 

 Peach leaves. 



The under surface of the leaves is occupied by the external manifesta- 

 tions of the fungus, but the mycelium penetrates the leaf. The glaucous 

 appearance of the hollows of the blisters consists of tufts of small 

 cylindrical cells, or asci, each containing eight small ovate uncoloured 

 sporidia (5 /j. diam.). When these sporidia are mature the asci are ruptured 

 at the apex, and they escape. 



