Orlovich, Drinnan & Ladiges, Floral development in the Metrosideros group 
703 
stamens are formed around and directly in front of those first formed (Fig. 13e-h), 
resulting in vertical rows of stamen primordia. The outer rows of stamens appear more 
or less evenly spaced in immature buds (Fig. 13i). Swelling of the petal bases gives the 
appearance of stamen clustering around the petals in the outer stamen row of more 
mature buds (Fig. 13j). Expansion of the hypanthium as the flower enlarges results in 
the spreading-out of the stamens to form a ring in the mature flower. Because there is 
relatively less hypanthial expansion in the antepetalous regions, stamens are less severely 
displaced from their position of insertion, thus they appear several rows deep. 
Xanthostemon verticillatus (C. White & Francis) L.S. Stnith 
Petals are initiated on the inside of the floral tube (Fig. 14a). Stamen primordia are 
initiated directly on the flank of the invaginated floral tube in front of the petals 
(Fig. 14b). The hypanthium expands and the outer row of stamen primordia form a 
ring around the hypanthium (Fig. 14c). Subsequent stamens are formed in vertical 
rows in front of the first-formed ones (Fig. 14d-g). The outer row of stamens appear 
to be clustered around the petals due to increase in size of the petal bases (Fig. 14h) 
and small clusters of colleters in the antesepalous positions (Fig. 14i). The stamens 
form an outer discontinuous ring (Fig. 14i) in which there are no stamens in the 
positions immediately opposite the sepals. 
Lysicarpus angustifolius (J.D. Hook.) Dnice 
Mature flowers have a ring of stamens around the rim of the hypanthium, and 
clusters of stamens opposite the petals (Fig. 15). The first stamen primordia are 
initiated on the inner wall of the floral tube as it develops subsequent to petal 
initiation (Fig. 16a). There is no pre-staminal bulge; stamens are initiated directly on 
the hypanthium in an irregular order as new space becomes available. Up to 60 
Fig. 12. Xanthostemon oppositifolius. Mature half flower (x 8.1). (from DAO 221). 
