DISEASES OF LIME AND OTHER CITRUS TREES 207 



curved, continuous or i-septate, 16-32 X 6-12 microns. The my- 

 celium is hyaline at first, darkening later. 



The galls are approximately round, attached by a broad base, 

 and vary from the size of a pea to knobs 2 to 3 inches in diameter. 

 They are at first covered by smooth green bark ; later by a 

 modified corky bark, which may crumble away leaving the 

 wood bare. 



Similar excrescences have been met with on lime trees m 

 Dominica and St. Lucia, and examined by F. W. South and by 

 the present writer. They have been strictly sporadic cases, 

 confined, in each instance seen by the writer, to an individual 

 branch of one tree in a cultivation. The branch is hypertrophied 

 in the sense of producing several abnormally long and thick 

 shoots, and the galls are usually associated with the buds along 

 the course of these. No fungus could be found suggestive of 

 the Jamaica species, nor any which would reproduce the disease 

 from inoculations. Galls occur in a similar way now and again 

 on cacao trees (see p. 176). 



It would appear that the Jamaica disease is not present m 

 these islands, and that the galls which do occur are not of an 

 infectious nature. 



Anthracnose of Lime. 



(Wither-tip, Blossom Blight, and Fruit Canker.) 



This is a very destructive disease of lime trees, in which the 

 ringing and tip-wither of new shoots, the infection and curling 

 of tender leaves, the blighting of buds and flowers, the loss of 

 newly set fruit, and the production of cankers on fruits which are 

 retained, are due to infestation with the fungus Glceosporium 

 limetticolum Clausen. 



History and Distribution. 



The identity of this fungus, and its specialised parasitism 

 on the lime and lemon have only in comparatively recent years 

 emerged from confusion with Colletotrichum glceosporioides Penzig, 

 which is very widely distributed on citrus trees generally, and 

 has been variously regarded as a dangerous parasite and as a 

 harmless saprophyte. The latter fungus (see separate account) 

 is common in these islands, doing Uttle recognizable harm, 

 whereas the affection under notice has been absent so far as is 

 known from the islands lying between Trinidad and Porto Rico 

 until its appearance and rapid extension in Dominica in 1922. 

 Recurring heavy losses of the nature indicated in the introductory 

 paragraph occur in British Guiana, where they have been attri- 

 buted to the direct effects of wet weather, but specimens received 

 in April, 1919, were found to be heavily infested with a fungus 

 indistinguishable from G- limetticolum An epidemic of the 



