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The Frequency of Anticlinal Divisions in Fusiform Cambial Cells of Chamaecyparis
M. W. Bannan
American Journal of Botany
Vol. 37, No. 7 (Jul., 1950), pp. 511-519
Published by: Botanical Society of America, Inc.
Stable URL: http://www.jstor.org/stable/2438026
Page Count: 9
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Study of the succession of tracheid rows in the secondary xylem revealed more rapid multiplication of fusiform initials in the cambium than hitherto assumed. Fusiform initials divided anticlinally not once every 15 years as estimated by Priestley, but as often as three or four times a year when growth was vigorous. The continuous production of new initials was accompanied by elimination which sometimes went on almost as rapidly. Even in the cambium of old stems and branches, where annual increase in girth was slight, multiplication and disappearance of initials continued at a surprising rate. Some of the fusiform initials which vanished from the cambium probably underwent maturation, others were reduced by subdivision and shortening to units of small size, many of which became ray initials. Factors influencing the rate and nature of change in the cambium were vigour of growth, age of the cambium, and location in the tree. Except in vigorous young stems or branches most of the anticlinal divisions concerned in the addition of fusiform initials took place during the last portion of the growing season. Nearly all anticlinal divisions were of the so-called pseudo-transverse type, longitudinal divisions from the side occurring in less than 3 per cent of the observed cases. Owing to the continued additions and losses of fusiform initials the cell pattern in the cambium was constantly altering, but nevertheless the extensive intercellular adjustments were accomplished without preventing the formation of matching pit-pairs in the derived tracheids.
American Journal of Botany © 1950 Botanical Society of America, Inc.