REPORT OF THE BOTANIST 249 



SESSIONAL PAPER No. 16 



DISEASES OF PEAKS. 



' FROST BELTING ' OR ' FROST BANDS ' OF PEARS. 



(Plate I. b). 



The accompanying illustration represents the peculiar appearance of some Bous- 

 sock pears which were taken off a tree growing in an orchard, in British Columhia. 

 The pears, which were quite perfect specimens as regards size and taste, showed a 

 peculiar ' band ' or ' belt ' of brownish tissue just above the lower, broader portion of 

 the fruit, resembling the well-known ' russeted ' condition with which we are familiar 

 in the well-known 'Russet' varieties of apples and pears (Golden Russet, Sheldon, 

 Bosc). Medlars (Mespilns) as a general rule also show the 'russeted' appearance 

 spoken of. These pear fruits however, showed only russet ' rings ' about three- 

 quarters of an inch broad, while the remaining portions were normally green. Prob- 

 ably eighty per cent and more of the fruits of this variety showed this appearance. 

 It has been ascertained that apples like the common Golden Russet may be grown 

 without exhibiting the roughish brown surface, and in consequence this condition 

 may be considered as abnormal. Microscopical examination of ail kinds of russeted 

 fruits has shown that their appearance is due to the formation of corky cells, which 

 certainly cannot be considered as normal on the surface of these fruits. The forma- 

 tion of cork cells is invariably an indication of an irritation of some kind. They may 

 be produced artificially on any kind of fruit by very slight abrasions of the epidermal 

 cells. Hence corky-cell patches of more or less large dimensions frequently occur 

 when fruits ' rub ' against each other or against a branch. Chemicals also produce 

 similar effects. The most common spray injuries from Bordeaux mixture become 

 largely apparent by the formation of cork cells, likewise any substance that is likely 

 to act destructively upon the waxy covering of fruits, may produce similar effects. 

 Lastly, frost has been held responsible for the changes of the epidermal cells into cork 

 cells. In many fruits, the russeted appearance is now regarded as typical and while, 

 strictly speaking, their appearance is due to their tender epidermal cells being injured 

 by frost, nobody feels concerned about it. On the other hand, when any cause renders 

 an otherwise perfect fruit ' patchy ' it is natural that the grower should seek the 

 cause, as a drop in the market price is likely to result. 



The curious ' belt ' on the pears in this case is due, no doubt, to the influence of 

 low temperatures, which prevailed during certain days, as we were able to ascertain 

 from the thermometer readings for that locality kindly supplied to us by the Meteoro- 

 logical Station of the Observatory in Toronto. The curious feature of this case is 

 the fruits showing this characteristic ' belt ' only, of a very uniform size and at the 

 same place. Frequently one may observe, in these flask-shaped pears, the lower 

 broader half totally russeted while the narrow tapering portion remains green. In 

 some apples and pears we have observed the same phenomenon forming a ring just 

 around the calyx of the flower. Careful study of the reason for this difference in the 

 formation of the belts showed that some fruits of different varieties of apples and 

 pears are covered, in their very young stages, towards the calyx with dense masses 

 of fine hairs. Sometimes these surround the calyx only and any moisture that may 

 naturally be present through atmospheric conditions freezes and the underlying tissues 

 become injured. In some varieties of pears, the hairs cover the calyx end for the 

 greater portion of the fruit and a frost belt is produced just above them, tbe hairs 

 naturally providing a protection. If any one interested will carefully examine the 

 different fruits, this observation may easily be proved, especially in the case of the 

 Boussock pears. Varieties of fruits commonly russeted very rarely show any hair 

 covering. The injury thus shows itself of little consequence and growers need feel no 

 alarm. 



