Histogenesis of the venation pattern in the leaves ofPolyalthia longifolia

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Summary

The venation system of the leaf inPolyalthia is pinnate. The procambial precursors of the vein in the leaves originate in the elongated cells of the middle layer, which in turn owes its origin to the adaxial hypodermal layer middle layer, which in turn owes its origin to the adaxial hypodermal layer of cells during the marginal growth of the leaf. Secondary vein development proceeds from the midrib to the margin of the leaf and from base to the apex. The plate-meristem is composed of isodiametric cells at the time of formation of secondary veins. At inception, the secondary vein procambium is multiseriate generally. The development of the tertiary vein procambium is mostly simultaneous and sometimes progressive and differentiates as uni- or biseriate strips. The quarternary vein and minor vein procambium differentiates as mostly uniseriate strips simultaneously. The vein endings, which are simple and unbranched contain only xylary cells, and develop progressively. The interveinal parenchyma possesses the capacity to produce additional procambial strands for a considerable period in ontogeny. Each areole contains one or two vein-endings, which end in the neighbourhood of the oil cells.

Communicated by Dr. T. R. Govindachari,f.a.sc.