[Ultrastructural aspects of Parthenocissus tricuspidata (Planch.) (Vitaceae) "callus" kept in solid cultures (author's transl)].

The normal strain shows undifferentiated chloroplasts in opposition to the very well chlorophyllated "callus" which shows all the normal ultrastructural characteristics of the various organelles. The strain which has lost completely the capacity of chlorophyl synthesis shows a remarkable increase in the size and number of mitochondria. The tumor tissue shows deep lobulation in its nuclei as well as undifferentiated plastids in the cytoplasm. An increase of the smooth endoplasmic reticulum in the tumor tissue was also observed.