GENERAL PRA CTICEDISEA SES. 



is found in almond, apricot, cherry, nectarine, peach, and plum trees. Gum disease (gum- 

 mosis, gum-flux) is distinguishable by an exudation of thick gum clinging to the 

 branches of the trees where they have been affected. It is a highly-contagious 

 disease, and can easily be produced by inserting a little of the sticky substance under 

 the bark of the trees named, as found by Dr. Beijerinck, provided it contain spores 

 of a fungus Coryneum Beijerincki. These spores cannot unaided pierce thick bark, 

 and although they penetrate soft young shoots where there is no apparent wound 

 or abrasion of the external covering of the 

 bark, the spores do not gain access to trees 

 with a dense cuticle without a crack, wound, 

 or abrasion. The first visible sign of attack 

 in a young shoot is the appearance of a red- 

 coloured speck. The bark first dies, then 

 the wood. Sometimes there is no discharge, 

 the shoot simply having the bark discoloured, 

 shrunk, and destroyed. The exudation appears 

 dependent upon the formation of cambium 

 and starch granules, for when the growth 

 becomes somewhat firm, the " tears " of gum 

 are freely exuded. Soft branches (growths of 

 the previous season) infected in winter have 

 the bark completely killed around the buds. 

 In these affections there is seldom any notice- 

 able exudation; but gum fills the wood show* five spores, highly magnified,* the .first and 



channels, destroying the branch, or greatly last geminating; the bottom figure on the right 



shows branching mycelium of the fungus ; and on 

 enfeebling the growth above the affected the left is represented part of a branch and shoot 



part. Gum also flows from the fruits of trees 



afflicted with Coryneum. It appears to proceed from the stone, generally at the 

 suture side of the fruit, where it shrinks and gum exudes, and pervades its flesh, 

 rendering it hard and useless. Sometimes the fruit so affected falls prematurely, and is 

 always depreciated in value. 



The fungus luxuriates in trees grown under an identity of conditions which induce 

 canker ; therefore, what has been advanced under that head, in respect of health-favour- 

 ing conditions of soil, climate, and cultural management, applies equally to trees afflicted 



H H 2 



Fig. 62. COEYNEUM BEIJERINCKI, FUNGUS CAUSING 

 Gun. 



References: The figures at the top on the right 



