Development of the epiphyllous inflorescence of Phyllonoma integerrima (Turcz.) Loes.: implications for comparative morphology*

The inflorescence primordium of Phyllonoma integerrima (Turcz.) Loes. is initiated on the adaxial side of the leaf primordium. At about the same time, a vegetative bud is formed at the base of the same leaf primordium. The vascular anatomy is the same in the fertile and sterile leaves, except that in the fertile leaf an inflorescence trace departs from the midvein of the leaf at the point where the inflorescence is inserted. Neither the inception nor the procambial supply of the inflorescence provide evidence of “congenital fusion” of inflorescence and leaf. It is also argued that the idea of an “adventitious” origin of the inflorescence is not useful in this case. Consequences for our conception of shoot construction are pointed out. It is argued that positional changes in the initiation of organs is an evolutionary process that may have remarkable effects on plant construction.