In which herbaceous dicot, abnormal primary vascular bundles are found in the medullary region?
A. Casuarina
B. Bougainvillea
C. Boehmaria
D. Lantana

Hint: Ordinarily, the vascular bundles, in the dicotyledonous stem, are orchestrated pretty much in a ring. In any case, there are a couple of varieties where the vascular bundles are pretty much unpredictably dispersed in the parenchymatous ground tissue of the stem. They show abnormal vascular bundles in a different region.

Complete answer: Abnormal secondary growth in dicots doesn't generally follow the vascular cambium creating xylem within and phloem to the outside. The types of Bougainvillea show abnormal growth in the vascular bundles, with a progression of cambia ascending external the phloem. This is because of the abnormal inception of the cambium.
In types of Casuarina with multilevel whorls, each stem vascular group isolates radially into two at the site of a leaf follow division, and similar two bundles rejoin acropetally to where the following supplies a leaf.
The phloem and xylem in Bohermaria comprised long vascular bundles and shut chambers with somewhat radially prolonged medullary beam cells. Annular, winding and scalariform vessels were seen in the longitudinal part of every single considered example.
Lantana camara, ordinarily utilized as fancy, has spread around the world. So, option D is incorrect
Hence, option B is correct.

Note: The anomalous secondary growth was concentrated in roots and stems of two types of Bougainvillea. The anomalous cambia emerge progressively in the diffusive request, each starting among the subordinates of the previous cambium. Every cambium layer works bidirectionally delivering xylem towards within the hub and phloem towards the outside. The arrangement of the creation of vascular cells is the accompanying: (1) conjunctive tissue and xylem strands towards within; (2) phloem towards the outside; (3) extra xylem with vessels towards within and extra phloem towards the outside.