The Coronal Rays of Passion-flowers

Abstract

THE filaments, or rays, forming the corona of Passion-flowers are structures of much interest. In 1790, Sowerby described them in Passiflora cærulea as a “double row of horizontal, thread-like, radiated nectaries.” His subsequent remarks, however, do not assure us that he regarded them as glandular, or as nectaries as we now define them. In Dr. Masters' “Contributions to the Natural History of the Passifloraceæ” (Trans. Linn. Soc. xvii.) no mention is made of distinct glandular structure, but Morren's opinion is quoted that “the corona is the seat of the perfume of the flower in Passiflora quadrangularis—a fact which he considers proved by the anatomical structure of the coronal threads, as also by the circumstance that if the processes in question be early removed the flowers remain scentless. In repeating this experiment, however,” continues Dr. Masters, “I have not been able to satisfy myself of the absolute correctness of this statement.… Prof. Morren attributes to the conical pimple-like cells of the epidermis of the coronal filaments the formation of the odoriferous principle. These peculiar cells are found on the surface of the petals, and in the nectariferous portion of the tube of the flower.… We must await further evidence before we assume that in the Passion flowers these cells really secrete the odorant principle.” In Vines' “Students' Text-book,” recently published, an emphatic statement is made that the coronal rays “are not glandular.”