Carina may perform a similar office, and then the aestivation is carinal, as in the Judas-tree (Cercis Siliquastrum).
The vascular bundles themselves are collateral, the xylem consisting of the protoxylem, towards the centre of the stem, and two groups of xylem, between which the phloem is situated; the protoxylem elements soon break down, giving rise to the carinal canal.
Only the median or carinal strand of xylem is common to stem and leaf; the lateral cauline strands possibly represent the remains of a centripetally developed mass of primary xylem.
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