Orlovich, Drinnan & Ladiges, Floral development in the Metrosideros group 
715 
d area of 
minimal 
expansion 
e 
Fig. 23. Diagram illustrating the pattern of stamen initiation and hypanthial expansion in 
XanthostemonjU/sicarpus-type flowers, a, stamens are initiated directly on to the floral tube 
centripetal to the petals; b, expansion and elongation of the floral tube allows more space for 
the initiation of more stamen primordia; c, numerous stamens may be formed provided there 
is sufficient space on the floral tube; d, expansion of the hypanthium prior to anthesis occurs 
chiefly in the antesepalous region; e, hypanthial expansion results in the antesepalous stamens 
being spread out into a single row of more or less evenly spaced filaments whereas the lack 
of expansion in the antepetalous regions results in there being more than one row. 
