Comparative stereoscan electron micrographs of nematode heads.

among the treatments from the water agar plates. Percentages did increase substantially, however, on N-free White's medium where p e r c e n t a g e s o f n o d u l a t i o n w e r e approximately two times higher for intact roots (59-61) when compared with excised roots (28-30). Nodules formed on roots in each experiment were tested for nitrogen fixation using the method of Koch and Evans (4). Reduction of acetylene to ethylene by nodules taken from all treatments confirmed nitrogen-fixing capabilities. R. japonicum or its metabolic by-products supported enormous populations of P. lheritieri in l abo ra to ry cul tures . A superabundance of a bacterial food source may account for passage of bacteria. Nematodes also can transport bacteria which adhere to their external body surface (3) as well as by ingestion and defecation (1). Since our data were not obtained from treatments beginning with equal concns of R.japonicum, Research Notes 131