PLANT DISEASES. 



733 



alimentary canal of an animal without being injured. The ultimate fate 

 of such spores is to be carried back to the land in manure. 



It may be argued, and with reason, that it is impossible to burn 

 everything bearing spores. This is true, but I consider it my duty, 

 nevertheless, to indicate clearly one of the most frequent sources of 

 fungus diseases. It remains with the practical man, armed with this 

 knowledge, to devise some means of meeting the difficulty. 



Even this problem can to a great extent be solved, and an epidemic 

 prevented, by adding a sprinkling of kainit to the manure each time it is 

 moved. Kainit is in itself a good manure. It will not kill either 

 sclerotia or resting-spores, but when these bodies commence to germinate 

 it will kill every germ-tube, also other mycelium present in the manure, 

 that it comes in contact with. Various other fungicides do the same. 



Tomato diseases have of late years been much in evidence. One of 

 these, the sleepy disease," has already been dealt with in this Journal 

 (Vol. xix. p. 20). Two others. Tomato leaf-rust {Cladosporium 

 fulvum) and Tomato black-rot or black-stripe (Macro spor mm tomato), 

 are very destructive. The former attacks the foliage, and in severe cases 

 the young fruit also. It appears under the form of a very short pile or 

 felt of a reddish brown colour, and consists of a miniature forest of 

 innumerable branched threads, each bearing several spores at or near the 

 tip. These spores become free when ripe, and are diffused by wind, or 

 very frequently by syringing before their presence is detected. Each 

 spore alighting on a damp Tomato leaf is capable of producing a new 

 disease centre, and after the pest has once gained a foothold only the 

 most persistent measures can check its spread. This is a case for spray- 

 ing, the object and methods for the proper conduct of which will be 

 explained later. Pale yellow spots on the upper surface of the leaf are 

 the earliest indication of the presence of this fungus, and when it bursts 

 through to the surface of the leaf to shed its spores it is sufficiently con- 

 spicuous to attract attention. Neglect in removing diseased leaves, or 

 entire plants where the evidence of its presence is undoubted, will result 

 in disaster. 



Black-rot can also be successfully combated by prompt and constant 

 removal of diseased portions at the earliest moment of appearance, aided 

 by spraying. 



IV. — Diseases of Fruit and other Trees. 



The fungi attacking living trees may be, as a matter of convenience, 

 divided into two groups : the large, woody, and often perennial forms, 

 including Polyporiis, kc, growing on the root or trunk ; and the small, 

 mostly microscopic kinds, met with on young shoots, leaves, and fruit. 



All the larger forms agree in being what are termed wound-parasites, 

 which means that when the spores germinate the germ-tubes cannot 

 directly penetrate an unbroken surface of the tree, but can only gain an 

 entrance through some wound or broken surface. Hence the importance 

 of carefully protecting all cut surfaces with a coat of tar immediately 

 after pruning ; branches broken by wind should also be removed, and 

 holes made by woodpeckers, &c., filled up. The Poli/poms most 



