Stern 'chips' from large-diameter stern regions of Larix laricina were produced free of contaminating organisms. These chips, consisting of dormant vascular cambium sandwiched intact between mature xylem and phloem, were grown as in vitro cultures on the surface of an agar medium that supports apparently normal cambial cell division and xylogenesis. It was determined that auxin (l-naphthaIene acetic acid) together with nutrients at low concentrations in the medium was essential for cambial growth, whether chips were grown in continuous light or darkness. Fusiform cambial cells underwent successive periclinal divisions to produce radial files of enlarged, bordered-pitted, secondary-walled, lignified and autolysed earlywood tracheids. As many as 20 new tracheids per radial file were produced, and > 95% of these were autolysed after 35 days of culture.