Bayer & Kubitzki, Inflorescence morphology of Lasiopetaleae (Sterculiaceae) 
727 
It is well known that the delimitation of inflorescences in woody plants can be a most 
difficult task. This is even more true when the application of Troll's (1964) concept of 
synflorescences is attempted. This is not surprising, because Troll's concept was 
developed upon the study of predominantly herbaceous plants and in temperate regions 
(Briggs & Johnson 1979), and the application of this concept to tropical woody plants 
is often difficult. If their growth is rhythmic, the growth flush may provide comparable 
units (Pilger 1922) and may serve to delimit synflorescences (Weberling 1983). 
In Lasiopetahm, Classen (1988) tried to delimit synflorescences in accordance with the 
concepts of Troll (1964), selecting three different reiterative parts of the flowering 
region as units of reference; 1. the module, which is the smallest recurrent unit; 2. the 
seasonal growth unit (sensu Briggs & Johnson 1979), which includes several modules; 
3. the perennial flowering shoot including its basal vegetative portion and the seasonal 
growtlr units of several years. As a result, the description of the inflorescence necessarily 
depended on the extent of the unit chosen. However, the typological classification of 
the synflorescence remains unaffected since the flowering zone of Lasiopetalum (Classen 
1988) and of other Lasiopetaleae can be characterized as monotelic in either of the 
three cases, even if the delimitation of a synflorescence is ambiguous. 
Systematic implications 
In a search for evidence for the assumption that the Lasiopetaleae are closely related 
to the Byttnerieae (Schumann 1895), a comparison of the inflorescence morphology in 
both tribes seems to be useful. There is a striking agreement in the position and 
structure of the inflorescences of Kcraudrenia with those of Riilingia and Commersonia 
(Byttnerieae), each with displacements not only of the fertile bracts, but also of the 
sterile one. The correspondence is so far-reaching that the scheme of the inflorescence 
of Keraiuirenia (Fig. 1) is virtually identical with one of Riilingia (see Bayer 1994: 34). It 
seems probable that this type of inflorescence, in which two of the three bracts that 
precede the terminal flower are fertile, represents the basic condition in Lasiopetaleae. 
The other type, found in Tliomasia and other genera of the Lasiopetaleae, is supposed 
to be the derived condition. Jenny (1985) postulated relationships between Keraiidreiiia 
and Coimnersonia because of similarities in the structure of the gynoecium; according 
to him, Tliomasia, Giiiclienotia and Lasiopetalum are farther derived because of their 
tendency towards a reduction of carpel and/or ovule number, their tubular stigma, 
and their anther dehiscence by pores or short slits. Another indication in favour of 
regarding the Lasiopetaleae as an advanced tribe of the Sterculiaceae-Byttnerioideae 
is the tendency towards reduction of the petals. This applies also to Riilingia and 
Commersonia, where short staminal tubes and reduced stamen numbers exist (Diels & 
Pritzel 1904/1905). It is interesting to note that these genera include the only Australian 
representatives of the pantropical tribe Byttnerieae. In contrast, the Lasiopetaleae are 
of rather restricted distribution. According to Schumann (1895), they are endemic to 
Australia, with the exception of the monotypic genera Pimia (Fiji) and Seriiigia (New 
Guinea, Australia), and one species of Keraudrenia from Madagascar. All these facts 
would indicate that the Lasiopetaleae are derived from advanced Bythierieae-like 
ancestors, but the analysis of their precise phylogenetic relationship is still an open 
problem. With regard to inflorescence morphology and other characters (anther 
deWscence by longitudinal slits, presence of five carpels with free styles, numerous 
ovules, cf. Jenny 1985), Keraudrenia is one of the genera that have conserved several 
primitive states within the Lasiopetaleae. 
