DISEASES OF PLANTS. 263 



cavities near the pit. Where the disease has progressed further sunken 

 areas appear on the outside, while inside the fruit the black spots are 

 larger, often extending all around the pit. As the disease progresses 

 the fruit gradually shrinks and dries up, the skin remaining unbroken. 

 Microscopic examination of these parts showed the presence of large 

 numbers of motile bacteria. Pure cultures were made of the bacterium 

 and its characteristics were partly determined, as follows: 



" It grew slowly in beef broth and rapidly in a decoction of vine wood. On pep- 

 tone meat gelatin its growth was small and slow. On the vine-wood decoction, 

 solidified with 12 per cent of gelatin, it grew rapidly. In puncture cultures it made 

 a tack-shaped growth, white, granular, and raised top ; in streak cultures it made a 

 granular growth, consisting of small, round, white colonies. On potato it made 

 a light, yellowish growth and darkened the potato. It was motile, aerobic, and did 

 not color nor liquefy the gelatin. In form it was a small bacillus with rounded 

 ends, 1 to 1.7// by 0.7/<, generally single or in pairs." 



Inoculations with pure cultures gave negative results. The disease 

 does not seem to affect the fruit nor to injure it appreciably until it 

 commences to soften. It does not affect the oil-making varieties and is 

 probably not dangerous. The fruit on affected trees should be picked 

 early and used for pickling. 



Another troublesome disease of the olive is figured and described. 

 This disease begins at the apex and works toward the stem end of the 

 fruit. When the olives are cut one-sixth to one-third seems to be brown 

 and partially dried up. Numerous cultures made of the mycelial threads 

 taken from the interior of the diseased olives developed two fungi, one 

 a Macrosporium, the other an Alternaria. Both fungi are figured and 

 described at some length. The author suggests that spraying the trees 

 with Bordeaux mixture would probably prevent the spread of. the dis- 

 ease. As it seems so far to be confined to the variety known as Neva- 

 dillo bianco, this variety should be omitted in planting where the 

 disease is found to be prevalent. 



Alfalfa leaf spot, R. Combs (Iowa Sta. Rpt, 1896-97, pp. 155-160, 

 figs. 4). — The author gives an illustrated description of alfalfa leaf spot, 

 caused by Pseudopeziza medicaginis, and reports a number of experi- 

 ments made to determine the method of infection and also the parts of 

 the plant subject to attack. Bis experiments show that the spores of 

 the fungus may be carried by the air and that the disease is strictly 

 local in its attack, the mycelium being confined to a limited space on 

 the leaf. The author recommends the burning of all refuse in the field, 

 since the disease readily survives the winter. Frequent cutting of the 

 crop is also effective in holding the disease in check. It is thought 

 advisable, where, seed is obtained from suspected or known infested 

 regions, that it should be soaked in a 10 per cent solution of copper 

 sulphate before sowing. 



Report of the botanical department, J. 0. Arthur (Indiana Sta. 

 Rpt. 1897, pp. 25-34).— The author gives a brief resume of various 

 lines of investigation carried on during the year. The experiments 



