301 



Long'itiidinal cracks are produced in infected petioles. On twigs 

 and branches discolored spots occur which are followed by gum- 

 ming and the development of deep cracks. By the time the fruit 

 is half-grown the whole inflorescence has frequently become af- 

 fected, and the death of the stalks causes the fruit to drop. On 

 the fruit itself the first sign of the disease is a small water-soaked 

 area ; this spreads considerably, and an irregular discolored spot, 

 intersected with cracks, is eventually produced. The discolora- 

 tion extends for some distance into the flesh. 



All the commonly grown varieties are afifected, but in differ- 

 ing degrees. The disease has not been found on related indige- 

 nous trees. 



Extensive spraying experiments with various mixtures have 

 so far given no evidence of the possibility of control by this 

 means, nor have any other remedial measures proved effectual. 



The cause of the disease has been shown to be a rod-shaped 

 bacterium to which the name Bacillus mangifcrac has been given. 

 It is found in great abundance in the parenchymatous tissues of 

 the discolored areas. It does not affect lignified tissues. The 

 optimum temperature for growth of the organism under labora- 

 torv conditions is about 30 C. (86 F.). It grows very slowly at 

 45C. (113F.). 



Infection appears to be principally carried from tree to tree by 

 wind, and is distributed about the tree in rain-water dripping 

 from infested leaves. 



THE POISONOUS NATURE OF CASTOR OIL SEEDS. 



The following is a summary from the Journal of the Board of 

 Agriculture (England) of a paper on poisoning by the seeds of 

 the castor oil plant read by Kobert at the meeting of the Union 

 of German Experiment Stations at the end of 1913: 



"There is only one species of ricinus plant known to botany, 

 viz., RiciiiKS communis, L., but there are a number of varieties. 

 All the varieties tested have proved poisonous, no matter what 

 the size or color of the seeds. The poison is contained in the 

 shelled seeds and not in the shell, capsule, or oil extracted from 

 the kernel. The substance containing the poison is known as 

 ricin ; it is not visible as such in the oil-free kernel ; in quantity it 

 forms only 1 per cent of the dry, oil-extracted kernels. As, 

 however, ricin exceeds strychnine or arsenic in intensity, small 

 quantities only of ricinus seeds suffice to make a feeding stuff 

 poisonous, a single gram of the kernel mixed with several litres 

 of milk having proved sufficient to poison a calf. 



"Castor oil seeds are introduced into feeding stuffs in various 

 ways. In the first place the hedges of fields of ground nut and 

 sesame in the tropics are often of ricinus plants and the seeds 

 may thus get mixed with those of ground nut or sesame at har- 

 vest. During transport, in storage, and in unloading there are 



