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Telopea Vol. 6(4): 1996 
For example, the first and fourth petal are adjacent to each other in the flower, but 
the difference between their sizes remains evident for some time. The same is true 
for the second and fifth petal. Petals four and five, which are often in close proximity 
in their early development, are never very different in size. This is most easily seen 
in Lophostemou conferttis (see Fig. 2), and it is evident to some extent in all taxa. 
Three categories of stamen arrangement are present in mature flowers. Lophostemou, 
Welchiodaidrou and Tristaniopsis have stamens united into distinct, antepetalous fascicles; 
Xauthostemou and Lysicarpus have clusters of stamens in front of tire petals, but also 
have stamens distributed around the hypanthial rim in the antesepalous regions, 
Melrosideros collina has evenly distributed stamens that do not express any obvious 
clustering. The small amount of material available for Tlwlewpici queeuslniidica and 
Tristania neriifolia preclude confident assignment to any of these groups. The difference 
between these three conditions can be accounted for by different spatial and ternporal 
factors in the ontogeny of the flower, both during and subsequent to organ initiation. 
The genera that have their stamens united into a distinct fascicle are characterised 
by the formation of a pre-staminal bulge on which individual stamen primordia are 
initiated. This is best demonstrated by Lophostemou confertus. In this species stamen 
initiation is a relatively late event in early floral ontogeny, by which stage the petals 
Fig. 20. Tristania neriifolia. a, flower bud with sepals and petals (P) removed. Stamen primordia 
are arranged in five groups of approximately three stamens. The central stamen primordium 
in each group is opposite a petal and there is a gap between each group of stamens. The 
development of the central stamen primordium in each group is more advanced than that of 
the outer two. Note the occasional presence of stamen primordia (arrows) in the antesepalous 
position (x 50); b, mature flower with two sepals and petals removed. Stamens are fused into 
five groups of three stamens for approximately half of the length of the filaments. The central 
stamen in each group is longer than the other two (x 17). (from DAO 169). 
