The concept that the flower is a modified or a metamorphosed shoot for the purpose of reproduction is an old one and the concept is gradually developed through the past and is accepted at the present by a majority of morphologists.
Linnaeus expressed this idea in his Philosophia Botanica (1751) by the phrase “vegetative metamorphosis”.
This concept that floral leaves were a modification of vegetative leaves was further elaborated by Caspar Wolff and Decandolle.
The ‘ foliar theory’ of the flower of the earlier botanists is held today by many though modified in one form or other by other botanists. That the flower is a modified shoot, is only a figurative expression, and implies that the floral leaves are vegetative leaves and transformed to do a different function of reproduction, in the place of the ordinary function of photosynthesis.