Abstract
Conducting tissues at the base of primary roots in seven millets were observed. 1. Primary roots with a large diameter showed high values of < diameter of stele/diameter of root > (Table 1). The proportion of the cross sectional area of stele to that of root was high in Sorghum bicolor and Pennisetum ryphoideum, and was low in Echinochloa frumentacea and Coix lacryma-jobi (Fig. 2). 2. In every species examined, the number of both phloem pole and pericycle cells were proportional to the diameter of the stele (Table 3, 4). 3. The number and mean diameter of late metaxylem vessels were not always proportional to the diameter of the stele (Fig. 4, 5). The primary roots with a large diameter often had relatively few and small vessels as compared with the root diameter.
