Abstract
The particles of narcissus mosaic virus (NMV) are rod-shaped with a modal length 548 to 568 nm. (Fig. 1), and morphologically similar to those placed in the potato virus X (PVX) group by Brandes (1964). However, its inclusion in this group is uncertain, because it seems unrelated serologically to any other virus in the group (Brunt, 1966). PVX produces some characteristic cytological effects, so that sections of leaves of Nicotiana clevelandii infected with NMV were examined in the electron microscope to see whether they resembled cells infected with PVX. They did not, and in contrast showed a strikingly different distribution of virus particles.
The sections were of systemically infected leaves, picked 3 weeks after the lower leaves of N. clevelandii plants had been mechanically inoculated with NMV. The pieces of leaf were fixed and embedded in Epon, as described by Milne (1970). Thin sections, mounted on uncoated grids, were stained in Reynolds' lead citrate for 1 min. and examined in a Siemens Elmiskop 1A operating at 60 kV.