GENERAL PRACTICE. DISEASES. 



239 



are the ends of the club-shaped structures bearing brown spores, fixed by the narrow 



end to short erect stalks; and these are produced on a mass of closely- packed small 



cells formed by the division of the mycelium 



by cross walls as represented in Fig. 64. 



From the figure it will be seen that the 



spawn threads (or mycelium) do not penetrate, 



except a few branch threads, far into the fruit, 



but remain in the cells of the skin. Thus the 



fungus devastates the fruit, living on its sub- 



stance, and continues to grow in the fruit after it 



is removed from the tree, preventing its keeping 



and causing its premature decay. 



Nor does the fungus confine its mischief to 



the fruit, but it grows on the leaves and young 



shoots. These are attacked simultaneously with 



the fruit, and their substance being abstracted as 



well as their epidermal (skin) tissues destroyed, the leaves lose their elaborative 



and assimilative power more or less, according to the severity of the attack, and thus 



restricted, the vitality of the whole tree is impaired. 

 The young growths, greatly weakened and dis- 

 ordered, cannot form fruit-bearing parts perfectly, 

 or store food essential to floral development. Future 

 crops are more or less imperilled by attacks of the 

 fungus. The spots on the leaves and young 

 shoots are usually from J to \ inch across, and 

 branch from the centre tree-like, hence the specific 

 name dendriticum. 



In tne leaf of tlie a PP le tne fangUS first appears 



Fig. 63. CLADOSPOEIUM DENDBITICUM ON APPLE. 

 Showing cracking and general disfigurement. 

 First appearance a minute black speck ; 

 growth varied size of black spots ; cracking 

 running together in black patches. 



Kg. 64. CLADOSPORIUM DENDRITICUM OEOWmo 



UNDER MEMBRANE OF APPLE. A vi i i mi i_ 



, . , ., , . , . , as a minute black speck. This grows into a patch, 



Showing fungus between the skin and flesh 



of fruit. Central part spawn threads over cells and numbers of those prevent its development, 



of fruit ; club-shaped bodies issuing from ... 



spawn threads-" fruits" of fungus bearing causing it to become crimpled and malformed, as 



spores; lower blunt oblong shapes-cells of represented in the example on the following page. 



apple ; upper rectangular forms membrane or 



outside skin of fruit. The mycelium in the leaf, as in the fruit, 



remains almost wholly in the cells of the epidermis, and, spreading, the black spots 



