Some Effects of Photoperiod on the Biosynthesis of Phenylpropane Derivatives in Xanthium

in this report that C. nocturnum is both LD and LSD in its responses and that the previously reported critical day length is for the LD responses while the LSD response has a critical day length of between 12 and 16 hours. This more clearly defining of the 2 responses in C. nocturnum brings into focus the previously suggested questions as to whether a single hormone can he synthesized as a result of more than 1 stimulus, and if a plant can respond to more than 1 hormone (2). One of the approaches that may give further information concerning the nature of the responses is through the study of hybrids of C. nocturnum with closely related species. Such an investigation is in progress. Summary