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The stem anatomy and pattern of secondary growth in Ungulipetalum filipendulum (Mart.) Moldenke, Cissampelos andromorpha DC., Disciphania hernandia (Vell.) Barneby, Odontocarya vitis (Vell.) J.M.A. Braga, and O. tamoides (DC.) Miers are described for the first time. Their morphology shares features of wood anatomy in common with other Menispermaceae, highlighted by wide rays, pitted tyloses and enlarged vessel pits near the perforation plates. However, unlike other members of Menispermaceae with successive cambia, a single vascular cambium remained functional and showed normal secondary growth. Other characteristics distinguish them from species having stems with successive cambia, such as parenchyma proliferation, new axial segments and type of parenchyma. In fact, it is thought that this pattern of secondary growth indicates that the stem will not develop successive cambia. Since the absence or presence of successive cambia has phylogenetic importance, a methodology which focuses on the pattern...

In Ipomoea hederifolia L. (Convolvulaceae), internal/intraxylary phloem originated as isolated strands from the procambially derived cells after the formation of protoxylem and protophloem. Bands of internal phloem were apparent in the sixth internode after the development of metacambium. In the relatively thick stems several small arcs/segments of internal cambium ensues from the parenchyma cells between the protoxylem and internal protophloem. Though all the segments were active, some of them (two of them located opposite to each other) were relatively more active. Bidirectional differentiation of these segments gave rise to secondary xylem centrifugally and secondary phloem centripetally, resulting inverted vascular bundles. Rest of the internal cambium segments were unidirectional and formed only secondary phloem centripetally. Like external vascular cambium, the internal cambium was non-storied. Structurally, secondary xylem and phloem was composed of axial and radial system in which rays we...

Structure and development of included phloem was investigated in the stems of Calycopteris floribunda Lamk., of the Combretaceae. After the definite period of cambial activity, cells in the middle of the cambial zone began to differentiate into thin walled cambial derivatives which separated the cambium into outer and inner cambial segment at certain places. Rest of the cambium along with separated outer segment remained functionally active while inner segment became temporarily nonfunctional. Original circular outline of the cambial cylinder was restored by joining of outer segment with existing one whereas inner cambial segment got embedded resulting in production of an islands of included phloem in the secondary xylem. This process was repeated several times resulting in a number of phloem islands surrounded within thick walled secondary xylem. Differentiation of phloem elements was initiated only after the formation of thick walled xylem derivatives from the outer cambial segment. The segment...

Stems in Sesuvium portulacastrum L. (Aizoaceae) increase in thickness by forming successive rings of cambia that formed concentric rings of xylem alternating with phloem. The cambium is semi-storied and exclusively composed of vertically elongated fusiform initials while cambial rays were absent in the early part of the secondary growth. In the older stems some of the fusiform cambial cells undergo further division and develop into vertically upright rays. The first ring of cambium formed thick walled lignified elements centripetally and phloem centrifugally for a definite period. A second ring of cambium is developed from axial parenchyma cells located outside the phloem produced by the previous cambium. Prior to the complete differentiation of new cambial ring, these parenchyma cells divide bi-directionally to form additional parenchyma cells (referred here as secondary cortex) to the outer and inner side. Cells formed outside to the new ring formed secondary cortex, which served as a site for ...