The ultrastructure of plasmodesmata in the filamentous green alga, Bulbochaete hiloensis (Nordst.) tiffany.

The ultrastructure of the plasmodesmata found in the green alga Bulbochaete hiloensis has been examined by electron microscopy of ultra-thin sections. Unlike most other plasmodesmata that have been described recently, there are no internal components such as a desmotubule or a derivative of the endoplasmic reticulum. Each plasmodesma consists of a cylindrical connection between the plasma membranes of adjacent cells. The cylinder is constricted at each end to orifices which may be less than 100 Å in diameter. Within the cylinder the cytoplasmic face of the plasma membrane is lined with material probably consisting of helically arranged particles. The lumen here is 400-450 Å in diameter.The observations are discussed in relation to possible functions in intercellular transport.