Pflanzenkrankheiten. 255 



between Heterodera radicicola (Greef) Müller and its hostplants, it 

 seemed highly important to the writer to evolve some pure culture 

 method b}'- which the various developmental stages in the life cj^^cle 

 of the later could be observed continuously. After manj'- unsuc- 

 cessful attempts, such a method was found, and is described in the 

 present paper. Pfeffer's nutrient agar, a synthetic medium, gave 

 so much satisfactory results, that it was used exclusively. This 

 synthetic agar was also used for growing the host plants. By pre- 

 venting i'apid growth of the seedling so that the closing plugs of 

 cotton did not have to be removed from the tubes, tomatoplants 

 were kept sterile for more than a month and could in this manner 

 always be artificially infected with the pure-cultivated Heterodera- 

 organisms. M. J. Sirks (Haarlem). 



Cook, M. T., The southern bacterial wilt in New Jersey. 

 (Phytopathology. IV. p. 277 — 278. 1914.) 



A brief communication about an epidemic, which was very 

 destructive in 1913 to the potato crop of South Jersey; the in- 

 vestigation by the writer convinced him that this disease was the 

 southern bacterial wilt [Bacillus solanacearurn Smith). The most 

 observant growers noticed that the plants over considerable areas 

 would wilt during the day, revive at night, wilt again during the 

 second day, but very seldom revive a second time. The severity 

 of the disease on the potato in 1913 was probably due to the very 

 wild Winter of 1912—13 followed by the exceptionally dr}^ growing 

 season for the early potato crop. M. J. Sirks (Haarlemj. 



Harter, L. L. and E. C. Field. The stem rot of the sweet 

 potato. [Ipomaea batatas.) (Phytopathology. IV. p. 279—304. 1914.) 



Stem rot of the sweet potato is a disease of considerable im- 

 portance for batatas-growers, heavy losses are incurred through it 

 in some localities, notably New Jersey where the sweet potato is 

 the principal mone}?- crop, the loss in the field varies every year 

 from 10 to 50 per cent, and fields have been seen by the writers 

 where 95 per cent of the plants were killed. The disease results in 

 loss of stand and a decreased j^ield from those hills which have survi- 

 ved, although infected. The S3^mptomology of the disease is descri- 

 bed in detail. A number of organisms has been isolated from 

 diseased sweet potato stems and from the roots in storage, which 

 are very susceptible to storage rois. Isolated were the following 

 fungi: Fiisariiun batatatisWr., F. ovthoceras App. et Wr., F. oxyspo- 

 ruyn Schlecht., F. radicicola Wr., F. caiidatmn Wr., F. hyperoxyspo- 

 rurn Wr., Nectria ipornoeae Hals. (^ Creonectria iponioeae Seaver = 

 Hyponiyces ipomoeae Wr.) and Gibberella saubinetii (Mont.) Sacc. 

 With these organisms the writers have made inoculation experiments, 

 the results of which can be summarized as follows: Sweet potato 

 stem-rot is caused by either one of two species of Fusarium, viz. 

 F. batatatis Wr. or 7*". hyperoxysporum Wr. Both species have been 

 succesfuUy inoculated into Ipornoea hederacea, the wild ivyleaved 

 morning glory. The stem rot organisms are not parasitic on &gg- 

 plants, tomatoes, peppers, clover, Irish potatoes, Ipornoea piirpurea, 

 I. coccinea and /. lacunosa. All attempts to produce stemrot of sweet 

 potato and eggplants with Nectria ipomoeae have been unsuccesstuL 

 The following species of Fusarium which were isolated in connection 



