In the field of
plant systematics, he used criteria such as stem structure and/or
leaf arrangement as a basis of anatomical criteria. As a
plant physiologist, he conducted investigations on the movement of leaves, the curling of
tendrils, the effect of low temperatures on
seed germination and the influence of
ultraviolet radiation on flower formation. He was particularly interested in the botanical family
Piperaceae. and was co-editor of the '''' (Geneva). He held honorary degrees (
doctor honoris causa) from the universities of
Rostock,
Geneva,
Aberdeen and
Uppsala. ==References==