SCHIZOMYCETES. BACTERIA 115 



Upon different hosts the galls differ only slightly in form and 

 appearance. Moreover, they are generally located near the sur- 

 face of the soil in the region of the collar. A gall may, however, 

 develop above the surface, or at some distance below, upon the 

 smaller roots. Superficial galls are more common where the ex- 

 posed portions are subject to such injuries as those produced by 

 rodents or the implements used in cultivation. 



Development of the gall. Published results regarding the de- 

 velopment of these galls are based upon an examination of woody 

 plants. It is probable that important differences will be found in 

 the case of herbaceous plants. In general, the gall is an annual 

 structure, even On woody plants, beginning its growth with ex- 

 foliation in the spring and maturing more or less by the time of 

 leaf fall. When first observed the hypertrophies are small masses 

 of rapidly growing, almost translucent tissue, nearly spherical in 

 shape. According to Tourney, such galls, when developed super- 

 ficially in cultures, may become greenish from the presence of 

 chlorophyll. In any event, the clear white appearance is lost in 

 a few months and the gall becomes warty and browned. During 

 the latter part of the season, or during the winter, disintegration 

 results, apparently by a normal process of decay. As a rule, such 

 galls do not develop secondary galls from any portion of the old 

 part but are entirely destroyed. Young galls may, however, spring 

 from the collar or roots near the margin of the gall previously 

 formed, and thus the wounds and injurious effects are intensified 

 from year to year. In time the functions of the conducting 

 tissues are so interfered with that death of the parts above follows 

 gradually. In the South and Southwest, galls which begin to grow 

 rather late in the season may continue their growth throughout 

 another year. 



According to Tourney "when the gall first begins its develop- 

 ment, there is a pushing outward of a small area of the true 

 cambium, which is transformed into large hypertrophied paren- 

 chyma cells. ... In its youngest stages the tissue of the gall 

 is a mass of parenchyma with numerous minute areas of rapidly 

 dividing meristem scattered through it. The areas of meristematic 

 tissue are centers of growth. ... As the galls become older 

 these centers of growth increase in size and others originate in 



