230 Early Studies in Bacterial Plant Diseases 



More than a year ago I sent the Department of Agriculture specimens 

 of grape roots showing peculiar bunches or galls. This disease is known 

 throughout the Southwest as " crown -root gall " or root-knot. It is not 

 only found on the grape, but affects nearly every variety of fruit tree grown 

 in Arizona. It is especially injurious to the peach. The knots most fre- 

 quently form just below the surface and not infrequently grow to be two 

 or three times as great in diameter as the tree itself. They sometimes 

 appear, however, on all parts of the root, and even along the trunk a foot 

 or more from the ground. I have found them beginning to develop on the 

 roots of seedlings only two or three weeks from the pit. In a Nursery in' 

 Phoenix only a few weeks ago, several thousand one year old peach trees 

 were condemned and destroyed, all being affected with the root-knot. 

 After reaching a certain size, the knots seem to cut off the flow of sap to 

 the parts above, causing the side of the tree on which the knots develop, 

 to die. Even in the later condition, in walking through a peach orchard, 

 those affected by the root-knot are easily recognized by the dark, dull, 

 appearance of the bark, and the distorted buds. Six or seven-year old 

 orchards last year lost from ten to twenty per cent of the entire number of 

 trees, and from all appearances as many more will die during the coming 

 season. The old knots are brownish black and easily crumble in the 

 fingers; the young knots are white, soft and full of sap. 



Knowing that you have been working on the peach for the last three 

 years, I thought likely your attention had already been called to this 

 disease, and that you could give me information regarding investigations 

 that have been made in the study of this knot. I enclose with this letter 

 a few specimens cut from peach roots. 



Smith had wanted to renew his indoor laboratory investigations 

 of peach yellows and other diseases of agricultural crops. On 

 October 9, 1892, while at Still Pond, Maryland, he had written to 

 Galloway: 



Am looking over the orchards once more, and for the last time I trust 

 to get the ups and downs of the disease by years, in varying seasons. 



As soon as this year's field work is wound up, I want to begin in the 

 same thorough way on laboratory work, and as a preliminary, I made out 

 a list of lenses and other accessories which will be necessary as soon, 

 almost, as I start in on it, and which I wish you would order for me as 

 soon as possible, so that the whole winter may not be lost in waiting for 

 them. I want to study the diseased protoplasm and can't do much without 

 the best appliances. The mechanical stage is for photographing. With it 

 I can use my stand for that purpose. 



Will try and get along with VanDieman's microtome, which I suppose 

 we can continue to use, but it will be necessary to have one or two extra 

 knives. We ought to have one at least which shall always be in good 

 order and never used on anything but sojt tissues. 



