GALLS 



387 



walled often homogeneous parenchyma, while in other cases the cata- 

 plasms are marked by the absence of any definite form, or size. Almost 

 all phytocecidia, or plant-induced galls, are cataplasmic. The swell- 

 ings on the roots of various members of the CrucifeejE caused by the 

 slime mould Plasmodiophora brassicce are of this nature. It is known 

 as Hanbury, clubroot, finger- and- toes by the practical grower of 

 plants. Root nodules, or tubercles, are produced on the roots of legu- 

 minous plants by bacteria (Figs. 153, 154, 155, 156), which can utilize 



Fig. 154. — Cross-section of root tubercle o£ Lupinus angustifoUus containing bac- 

 teria, X 46. {.ASier Moore, Geo. T., Yearbook Dept. Agric. pi. xxxviii, 1902.) 



free atmospheric nitrogen and by their activity the leguminous plants 

 secure large amounts of nitrogen. A species of Actinomyces, or ray 

 fungus, is probably the cause of the mycodomatia of Myrica. Bacteria 

 also cause tumors on the Pinus halepensis and Oka europtea, on the latter 

 in the nature of a crown gall suggested to be somewhat like animal 

 cancer (Figs. 157, 158, 159). Recently Erwin F. Smith in relation to 

 the abnormal multiplication of the tissues which result in a crown- 

 gall tumor, or hyperplasia, concludes that the removal of growth inhibi- 

 tions is brought about by the physical action of substances liberated 



