DISEASES OF PLANTS. 55 



onons to stock grazing upon their herbage. Macrozamia miquellii is considered 

 most injurious, as it is believed to produce in cattle a disease called ''rickets." 

 The disease causes a lack of control over the movements of the hind legs. Young- 

 stock in poor condition seem most subject to tlie disease. Affected animals may 

 improve, but they are said never to completely recover. 



DISEASES OF PLANTS. 



The olive knot, F. T. Bioletti (California Sta. Bui. 120, pp. 11, 

 ph. 3, fig. 1, dgm. 1). — The author reports the recent discovery in Mer- 

 ced County, California, of the disease known as olive knot, which is 

 said to be caused by Bacillus olece. Attention is called to the lack of 

 satisfactory curative measures and the importance of quarantine regu- 

 lations against infected nurseries or olive groves. 



This disease, which has been known for some time in Southern Europe 

 and elsewhere, seems to be widely extended, but the specific cause was 

 not known until 18SG, when the specific organism was separated and 

 the disease produced by means of inoculation. The disease was first 

 noticed in the orchard referred to above in 1893 on a single tree. 

 Since that time it has spread over a large part of the orchard. The 

 author visited the place in February, 1898, and made a somewhat lim- 

 ited study of the disease. In the orchard were 141 olive trees, G of 

 which have been destroyed, 13 are seriously injured, 09 show numerous 

 knots, while the remaining 23 show little or no evidence of disease. 

 While there is but little evidence upon which to base judgment rela- 

 tive to susceptibility, in this orchard some varieties seemed more resist- 

 ant than others, since some were not affected, although surrounded by 

 badly diseased trees. 



The roots of the trees seemed but little affected. On the trunks, 

 wherever there was a jagged wound, such as is made by breakiug off 

 a branch or a blow by a plow, the knots were very numerous, the edge 

 of the wound evidently serving as a place for infection. Occasionally 

 small tubercles, varying from the size of a pin head to that of a pea, 

 are found on the leaves, generally on the under side. The occurrence 

 of affected leaves is very irregular, some of the most badly affected 

 trees showing no tubercles on the leaves. The effect on the fruit could 

 not be definitely ascertained. The owner of the orchard stated that 

 the fruit seemed to be affected, as many olives rotted while undergoing 

 the process of pickling. The nature and symptoms of the disease are 

 given at some length, largely quoted from Savastano's description. 1 



The author conducted some experiments in a laboratory with knots 

 collected during the winter at the time of his visit, but the material was 

 very unfavorable, most of the knots being old and dry. However, a 

 few were found which were still unbroken, and from the interior of 

 these cultures were made, five of which agreed morphologically with 

 the organism to which has generally been attributed the cause of the 

 disease. 



Compt. Rend. Acad. Sci. Paris, 1013 (18SG), p. 1111. 



