GALLS AND TUMORS 609 



the tendency of the leaves to wilt or turn yellow when an examination 

 of the roots will at once reveal the distinctive features of the disease. 



The spores are hberated with the disintegration of the diseased roots 

 and become disseminated in the soil during cultivation. Under ap- 

 propriate conditions the spore is ruptured and a small flagellated, 

 amoeboid organism emerges. It is in this form that the parasites 



Fig. 148. — Roots of Cabbage plant showing characteristic hypertrophy due to 

 Plasmodia pkora hrassicat. {Woronin.) 



penetrate the roots of the young plants in which they complete their 

 development. The youngest forms seen within the vegetable cells 

 possess two nuclei each with a central mass of chromatin or karyosome. 

 Several organisms frequently invade a single cell. As they grow there 

 is a multipUcation of nuclei and the associated organisms tend to fuse 

 together to form plasmodia. Subsequently there occurs a series of 

 changes, certain stages of which are readily distinguished but also 



38 



