124 THE OLIVE 



HOXEY DEW. 



The Honey dew consists of a gummy sugary perspiration on the 

 leaves, especially on the under side, on the flowers, and on the youno- 

 branches. This substance sometimes forms itself into a varnish uni- 

 form in its deposit, and at others into drops like dew. This disease 

 attacks the Olive, Poplar, Linden, Orange, Walnut, Willow and 

 Elm trees and also the grape vine. The real cause of it is un- 

 known. Some writers think that the viscous matter is exuded from 

 the cochineal insect which infests the plants, but others have observed 

 that this disturbance exists both on trees in the open air, and on 

 those enclosed in greenhouses where there were no insects. 



The popular idea is that the humor emitted by the morbid leaves 

 is a production of the plant itself, caused by the unfavorable influence 

 of a hot, dry soil. Admitting this to be the probable cause, the remedy 

 would be copious fertilizing and to prune the tree so as to keep the 

 top in proportion to the spread of the roots. 



SCAB. 



The scab manifests itself in wart-like excrescences as large as wal- 

 nuts, often affectins: the vounsiest and most slender branches. Tiie 

 plant impoverished by this pest takes on a languid appearance and 

 sometimes dies. Ordinarily this evil is met with on soil that is low 

 or too rich and not .sufficiently ventilated, or where trees are 

 placed too near together, in trees excessively pruned, or in those 

 maltreated in the o-atherins; of the fruit bv beating with poles. 



Some writers hold the opinion that the scab is caused by either a 

 vegetable or animal parasite, but the most diligent microscopic ob- 

 servations have never revealed the presence of an insect, either be- 

 fore, after, or contemj^oraneonsly with, the ajDparition of the small 

 protuberances. The cause therefore must arise from some disturb- 

 ance of the functions provoked principally by contusions, either irom 

 hail storms or by poles in beating down the fruit, by excessive prun- 

 ing, or by absence of light and air. The contusions of the cortical 



