94 
PHARMACEUTICAL BOTANY 
extend into the middle cortex cells carrying the bacteria with them. 
Within the cortex cells the organisms multiply rapidly producing 
nest-like aggregations. Their presence here causes the formation of 
nodules or tubercles. Under oil-immersion magnification these 
bacteria are found to exhibit variously shaped involution forms called 
bacterioids. They remain within the cells of the medio-cortex region 
Fig. 38. — Root system of a legume showing tubercles. (Marshall.) 
gradually swelling up into zoogloea 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. 
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. 
