Letters to the editor

The fine structure of the colonial volvocacean alga Eudorina illinoiensis (Kofoid) Pascher is described in detail, excepting the eye spot. The structure conforms closely to the Chlamydomonas type and helps confirm that certain ultrastructural features are peculiar to certain taxonomic groups, the characteristic structure of the transitional region of the flagellum being an example in this case. A spiral filament around the outer doublets of the axoneme is newly reported.

Particular attention is given to the flagellar apparatus and to the structure of the chloroplast in relation to the pyrenoid. Small stacks of thylakoids pass between the starch plates to enter the pyrenoid where they assume a tubular form. The spatial re-organisations required to achieve this are described.