Date of Award

Spring 2004

Document Type

Restricted Thesis

Terms of Use

© 2004 Emily S. Ford. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts



First Advisor

Colin Purrington


Although some investigation has been conducted on the extent of handedness bias in twining vines, the proximate and ultimate causes of handedness preference in the plant kingdom have long remained unexplained. Studies on the distribution of twining handedness have shown a nearly universal preference for unidirectional, species-specific twining, the majority of which is counter clockwise (CCW). To investigate the origin of the CCW bias, the evolution of twining direction was studied. Additionally, the potential advantages to CCW twining and the effects of environmental cues and regional variation on twining were probed using a vine facultative in twining direction, Solanum dulcamara (Solanaceae, Nightshade Family). To determine the causes of handedness in twining vines, the relationships between chiral cellular components, other plant enantiomorphies and twining were investigated. Mapping of twining handedness onto an angiosperm phylogeny revealed multiple evolutionary origins of twining habit and handedness, potentially indicating multiple determinants of handedness. CCW twining plants were shown to have tighter coils than clockwise (CW) twining plants, and the choice of twining habit, though not direction, was influenced by the location of seed Oligin. Finally, the direction of circumnutation (rotational growth pattern observed in developing seedlings and shoots), spiral phyllotaxy (leaf arrangement), xylem helices, and cortical microfibrils (cytoskeletal elements known to form helices) were not associated with the handedness of the vine.