Hypothetical plant hormones are:-
(a) florigen (b) vernalin
(c) florigen and vernalin (d) auxin
The commonly recognised class of plant hormones are auxin, gibberellin, cytokinin, ABA and ethylene. Some scientist believes that flower initiation is controlled by plant hormones callen florigen. A German plant physiologist George Melchers has also proposed the existance of vernalin (i.e., vernalisation initiating substance). Both these hormones are not been isolated so far. So, it still remains to be a hypothetical chemical.