The Vascular Cambia of Dodder and its Allies

Abstract

The vascular cambia of 20 species of the dodder and its allies belonging to the CassythaceaE, Convolvulaceae and Cuscutaceae were surveyed to assess their phenetic and phylogenetic significance. In natural condition all of them contain anomalous cambia. The Cassythaceae bore transitory cambium in the normal position but atypical by asmmetric activity. (The Cambium alternatelt retards accemtuates xylem formation on several segments and there are profuse sehizongenous spaces in wood. Haustoria contains both traheids and vessels).

In stems and roots of the Convolvulaceae a series of widely different anomalous cambia were found which sometimes differed in stems and roots of the same species. Stems of arborescent group had bands of interxylary phloem in concentric rings, while in the primitive twiners these are arranged in radial plates. In general, a tendency was to increase the proportion of soft tissue. In Cuscutaceae the specified anomaly was the interfascicular cambium. Ray initials were absent but fusiform initials differentiated into profuse parenchyma cells and a few vessel elements.

Haustorium develops only imperforate tracheary elements. The evolutionary history vascular cambium in the Convolvulaceae was mainly one of reduction in activity and area. Thus the vesselless haustorium of Cuscutaceae. may be regarded as a reduced farm in with the vessel bearing haustorium of Cassythaceae. It 1s also concluded that the primitive condition of Cuscutaceae is possibly derived from the general condition of Convolvulaceae.