Bryophyllum tubiflorum exhibits several kinds of phyllotaxis patterns: pseudo-bijugate, imperfect pairs, transition helix, imperfect trios, tricussate and inverted helix. Assumptions were introduced and computed in a computer model that these changes in phyllotaxis are due either to changing rates of production of an inhibitor on the apical surface, or alternatively to changing apical size. Observations on the structure of the apex supported the latter assumption. Mirror asymmetry in the position of the first two leaves was found necessary for the computer simulation, and was also confirmed by observation.