The wood structure of Dicranostyles (Convolvulaceae)

The anatomy of the mature wood of three species of the South American genus of woody climbers Dicranostyles Bth. is described and compared with that of the secondary wood of other genera of the Convohulaceae. The stems are characterized by the occurrence of concentric rings of included phloem tissue. In most characters the three species are quite similar, except for the absence of rays over two cells wide in D. guianensis. Instead of these, aggregate rays occur at intervals between consecutive rings of included phloem. D. mildbraediana possesses fibre tracheids with next to the normal large bordered pits numerous very large irregular slits giving the impression of a helical sculpturing of the walls. From a comparison with other Convolvulaceous genera like Bonamia, Ipomoea, Maripa, Neuropeltis, and Prevostea 1 it appears that nearest to Dicranostyles in general appearance as well as in anatomical structure is the genus Maripa. The resemblance to Ipomoea seems only superficial. The relation between anatomical conformities of genera and their position in the various systems of subdivision of the family is discussed.