104 VEGETABLE PARASITES AND EPIPHYTES 



one or more " humps " are formed which, when cut in 

 section, show brown streaks in the affected tissues. Such 

 fruits never ripen, but fall before they are half grown. 

 Other disease-infected fruits show one or two black 

 blotches, the tissues of the shell are stone hard, changing 

 first to a brown and later to a black colour, and 

 eventually die. These fruits may contain beans which 

 are apparently sound, together with several mucila- 

 ginous beans. 



Another symptom of the disease is that of " Star 

 blooms," which consists in the production of a large 

 number of flowers crowded together, vegetative shoots 

 developed into small "witches' -brooms " being frequently 

 found among the flowers. The " cushions " from which 

 the flowers arise may be hypertrophied, from which spring 

 side shoots that branch and give rise to fascicles of flowers. 

 Fully developed fruits are rarely produced from ' ' Star 

 blooms," but irregularly shaped fruits are sometimes 

 formed, which on being cut in section are found to 

 consist of a thick rind with five small cavities devoid 

 of beans. 



It is considered that infection of both twigs and flowers 

 takes place only at very early stages of their develop- 

 ment, and that this is effected by spores which fall on 

 vegetative buds or on the cushions from which flower- 

 buds issue. 



The productive capacity of certain trees is diminished, 

 while others die from the effects of this disease. 



Before the outbreak of the disease in Surinam 

 the average yield of cured cocoa was estimated at 

 440 Ib. per acre; in 1904 the yield had fallen to 

 72 1 Ib. per acre. The area under cocoa cultivation 

 had decreased from 15,828 acres in 1903 to 13,481 

 in 1908 as a result of the abandonment of diseased 

 plantations. 



Owing to the decreased vitality of affected trees they 

 are rendered more susceptible to the attacks of the 

 "cocoa beetle" (Steirastoma depressum). 



With regard to trees dying, it seems possible that in 

 most cases Thyridaria tarda is eventually responsible for 

 death, as it enters the dead " brooms " and then pene- 

 trates into the living tissues. 



Young plants, placed out in the vacancies caused by 



