Mar. 4. 1918 Wilt Diseases of Okra 539 



sterilized soil in the greenhouse, or in soil new to these crops in field 

 plots. Soil inoculations were made by pouring a few cubic centimeters 

 of a sterile-water spore suspension of the organism to be used on the 

 steam-sterilized soil, either before or after planting the seed, or in the 

 vicinity of the seedlings. The majority of the inoculations were made 

 through wounds at the hypocotyl below the soil level. The wounds 

 were made with a sterile scalpel, and after the inoculum was intoduced, 

 the soil was replaced to prevent drying. A few inoculations were made 

 through wounds made by breaking off leaves and pods of the okra plants. 



Approximately as many control plants were prepared as plants for 

 inoculation. Half of these were wounded or otherwise subjected to the 

 treatment employed on the plants inoculated, and the other half were 

 left as imwounded controls. For the wounded controls, sterile water 

 was used for inoculating, in lieu of the spore suspension. Wilting plants 

 were examined microscopically for mycelium in the xykm of roots, 

 stem, or petioles; and pure cultures of the organism used were reisolated 

 and identified as a control on the work. Frequently such reisolated 

 strains were used for subsequent inoculations. 



In but one experiment was there any wilt in the controls. In this 

 case after six weeks 6 per cent wilted, and the organism used in the 

 experiment was recovered from the interior of the plants. However, 

 this was a field test and there was in the duration of the experiment 

 an opportunity for infection from inoculated plants in the adjoining 

 rows on either side. 



INOCULATION OF VARIOUS ECONOMIC PLANTS WITH VERTICILLIUM 

 ALBO-ATRUM AND FUSARIUM VASINFECTUM 



Inasmuch as the inoculation experiments were carried on in a uniform 

 manner and controlled by a large number of wounded and unwounded 

 plants, as well as by reisolation and identification of the organisms 

 causing the disease, the results are comparable. For convenience these 

 results are brought together in tabular form (Tables III, IV, V) and the 

 discussion of the results of the inoculations are arranged according to the 

 host plant and the parasite used. 



HISTORY OF THE STRAINS OF VERTICILUUM ALBO-ATRUM AND FUSARIUM 

 VASINFECTUM USED FOR INOCULATION 



The history of the various strains of V. albo-atrum and F. vasinfectum 

 used for inoculating the several host plants is as follows : 



F. vasinfectum strain 1855. Reisolated from the vascular system of a 

 cotton plant, which was wilting as a result of inoculation with strain 1733, 

 a reisolation of strain 1635, which was in turn a reisolation of the original 

 strain 1485, isolated from the discolored vascular system of a wilting 

 cotton plant at Florence, S. C, in 191 2. 



F. vasinfectum strains 2708, 2709, 3203. Isolated from the discolored 

 vascular system of wilting okra plants collected at Florence, S. C. at 



