94 DISEASES OF CULTIVATED PLANTS 



" gall " and dispersed in the soil, are able at once to produce 

 the " crown-gall " of lucerne, and also to ascertain whether the 

 fungus can attack other plants, such as mangold, potato, etc.' 



During the winter of 1905-6 a number of badly diseased 

 lucerne plants, covered with galls, were obtained from a farm 

 near Herne Bay. These 'galls ' were kept dry in the labora- 

 tory through the winter, and a number were then taken from 

 time to time and first soaked in water, and then ground up in 

 water with a pestle and mortar. A drop of this water, on 

 being placed under the microscope, was seen to contain many 

 hundreds of the resting-spores of the fungus. 



Six well-grown and healthy plants of lucerne, beet, mangold, 

 and potato, in 9^ inch pots, were richly inoculated with the 

 spore containing water, the water being poured not only 

 over the crown of the roots and the surface of the pot, but 

 also into a number of vertical ' borings ' which reached to 

 half the depth of the pot. Six ' control ' pots of each kind of 

 plant were kept side by side with the inoculated ones. All 

 the pots were sunk in the earth in the experimental ground. 

 Later in the season the twenty-four inoculated pots were 

 again similarly inoculated. The dates of the two inoculations 

 were chosen so that, in the case of each of the four plants, 

 the first inoculation was made just as the first shoots 

 appeared above ground, and the second when the shoots 

 were full grown for the season. In November all the plants 

 were examined. On five out of the six inoculated lucerne 

 plants 1 a number of 'galls' had been produced. In two 

 cases the attack of the fungus had been so virulent that the 

 lucerne plant was actually killed. No formation of 'galls 3 

 occurred on the ' control ' lucerne plants, nor on any of the 

 inoculated or ' control ' plants of mangold, beet, or potato. 



The present disease has not been observed in England 

 previous to the Herne Bay case in 1906, and no fresh case 

 has since come under my notice. It will be well, however, 

 for farmers to keep a careful look-out for this new disease, 

 since in several countries on the continent, and also in South 

 America, it has proved to be very destructive to cultivated 

 lucerne. So far as the present investigations show, it is safe 

 to grow beet, mangold, or potatoes after lucerne which has 

 suffered from this disease. 



This is one of the numerous instances where the only safe 



1 These were two-year-old plants. 



