COLLETOTRICHUM 443 



investigation, and failed to corroborate the statement that it 

 was due to an Exoascus. I only found sterile mycelium, 

 which certainly did not belong to an Exoascus. At a later 

 date Dr. Van Hall and A. W. Drost, who were located in the 

 West Indies, and had ample opportunities for investigating 

 the disease in a living condition, have shown that disease is 

 not caused by a species of Exoascus, but by a fungus of a 

 totally different nature, on which they have bestowed the 

 name of Colletotrichum luxificum. The witches' brooms or 

 hypertrophied branches are, as a rule, recognised by being 

 much thicker than normal branches, the surface is irregular 

 and more or less undulated, and the thickened base marked 

 by longitudinal grooves. The leaves produced on brooms 

 never attain to the normal size, and remain soft and pliant, 

 and are often deeper in colour than the ordinary leaves. 

 Lateral branches are usually present, and as is usually the 

 case, the hypertrophied branches are more or less vertical in 

 growth. The brooms develop very quickly, and are dry and 

 dead within a short space of time. The inflorescence is also 

 attacked, resulting in the crowding together of a great number 

 of flowers, some borne on simple flower-stalks, in others the 

 flower stalks are much branched, and among the flowers 

 vegetative shoots often appear. Very few of these diseased 

 flowers produce ripe fruit, but the product is usually deformed, 

 small, and round in shape. Finally, the fruit is often also 

 attacked by the fungus, causing the disease known as 'black- 

 ening,' or 'hardening' of the fruit, which appears under the 

 form of a black patch on the fruit, and causes the tissue of 

 the affected part to become as hard as a stone. At such 

 points the seeds are spoiled, being closely surrounded by the 

 dried-up pulp as if mummified. 



The branches are infected when quite young, and the 

 mycelium permeates all the tissues of the branch, and also 

 enters the leaves. 



On hardened fruit or on the witches' brooms the fungus 

 forms minute fruiting pustules, dingy white or tinged rose- 

 colour, o-i-o^ mm. diam. Black or dark grey, multiseptate 

 and sterile hairs, tapering from base to apex, 50-120 \i long 

 stand erect amongst the conidiophores. Conidia hyaline, 

 oval or ovoid, sometimes slightly narrowed at the middle, 

 13-19 X 4-5 /*. The conidia are produced in chains. 



Diseased trees produce but little fruit, and eventually die. 

 A systematic removal of all diseased portions is recommended. 



