CAUSE AND NATURE OF CROWN-GALL li> 



found under infested trees. However, in most instances only 

 a small percentage of the seedlings growing under diseased 

 trees had galls upon them. This freedom was probably due to 

 the fact that the seedlings were usually growing at some dis- 

 tance from the boles of the trees where the galls most frequently 

 develop, and likely had not as yet come into contact with the 

 contagion from the old trees. 



A few seedlings of more than a year' s growth were found in 

 making this examination. A larger percentage of these were 

 diseased than of the seedlings that germinated and grew during 

 the previous summer. It is likely that many of the younger 

 seedlings, which at this time showed no evidence of galls, would 

 develop them at the beginning of the growing season, the com- 

 ing spring. It appeared that the conditions in the orchard were 

 not so favorable to the communicability of the gall as the con- 

 ditions in the green-house, where the moisture was much more 

 uniform. 



The percentage of diseased to perfect seedlings growing under 

 the old trees is strikingly shown in the diagram made to illus- 

 trate this point (Fig. 2). Although a comparatively small 

 number of the seedlings examined were diseased, their position 

 in relation to the galls at the crowns of the old trees is very 

 significant. 



A similar examination of seedlings in this orchard was made 

 December 21 of the following year. At this time about nine- 

 tenths of the trees had been dug up, those remaining being, 

 for the most part, adjacent to irrigation ditches. It was ob- 

 served at this time that most of the badly diseased trees had 

 very few, if any, seedlings beneath them. It is possible that 

 they had been previously killed by the action of the disease. 

 At the time of this examination one hundred and twenty-five 

 seedlings were dug from beneath the branches of diseased trees. 

 As the results obtained were practically identical with those of 

 the previous year, I do not present them in schematic form. 



I took occasion to examine the excavations from which one 

 hundred and thirty trees had been removed, and failed to find a 

 single one free from fragments of galls broken from the roots 

 when the trees were taken out. 



