PLANT ORGANS AND ORGANISMS 
I 33 
bacteria are found to exhibit variously shaped involution forms called 
bacterioids. They remain within the cells of the medio-cortex region 
gradually swelling up into zoogicea masses, until finally their bodies 
break down into soluble nitrogenous substances which are partly 
absorbed and assimilated and partly stored as reserve nitrogenous 
food for the green leguminous plant. 
Fig. 65.—Root system of a legume showing tubercles. {Marshall.) 
In the modern rotation of crops, plant growers plough under the 
leguminous crops or their nodule-producing roots which decay and 
enrich the soil with ample nitrogenous material to supply the next 
season’s crop of nitrogen-consuming plants. 
The writer has found tubercles on Myrica cerifera , Myrica Car - 
oliniensis and Myrica Macfarlanei seedling primary roots of 5 to 6 
months’ growth, and from thence onward on the secondary roots 
inserted on the hypocotyl axis, on nearly all the adventitious roots of 
subterranean branches and on the subterranean branches of Myrica 
