64 Fruits and Fruit- Trees. 



in the oozings from plum-tree sores, is referable, pri- 

 marily, to the operation of a minute parasitic fungus, 

 a species of Coryneum, which may be transferred for 

 experiment sake from one tree to another. Gumming is 

 thus to be classed with the maladies that plants are 

 subject to. There are plenty of illustrations of it, but it 

 is here perhaps, in the stone-fruit trees, that the student 

 of vegetable pathology finds his best opportunities for 

 investigating the causes and the results.* Another very 

 curious and interesting occurrence for the student, seldom 

 observable except in the Drupiferae, is the superseding, at 

 times, of the solitary carpel, by two, three, four, and even 

 five carpels, all of the same kind, an effort towards con- 

 formity with the quinary perianth. Instances of this 

 occur in certain species of cherry, in the double-flowered 

 plum, and the double-flowered peach. These extra 

 carpels stand side by side, unconnected if only two, 

 partially united when more, and every one of them 

 usually ripens. The native countries of the Drupiferae 

 are found almost exclusively in the temperate parts of the 

 northern hemisphere. Carried into the tropics, these 

 priceless trees are apt to become evergreen, and cease to 

 bear fruit. Where the date and the banana flourish we 

 must never look for the cherry, though the apricot is quite 

 happy in the oases of the North African deserts. 



It is important not to confound with the genuine stone- 

 fruits the somewhat similar olive, litchi, cornel, and 

 others, these belonging to quite different families, as will 



* For particulars, see the Gardeners' Chronicle, Feb. 23rd, 1884. 



