Grimes, Mimosoid legumes 
745 
Discussion 
No single generalized pattern of development of shoots and inflorescences has been 
found for the species examined. All species are alike in that the leaves are neoformed 
(versus preformed, see Brown & Sommer 1992), and axillary buds form within the 
first 8 plastochrons. They are also alike in that there are no morphological differences 
between sylleptic and proleptic vegetative buds (cf. Tomlinson 1978; Tomlinson & 
Gill 1973). Furthermore the axis of most shoots producing unit-inflorescences are 
persistent. The major differences in the species herein examined can be found in 
phyllotaxy, morphology of the axillary buds, and in timing of development of stipules 
and unit-inflorescences. 
Zapoteca tetragona and Lysiloma mkrophyUum both have distichous phyllotaxy, while 
Ebenopsis ebano, Acacia nilotica, Paraserianthes lopbantha and Pithecellobiiim duke have 
2/5 spiral phyllotaxy. Martinez (1975) also noted distichous phyllotaxy in Inga 
uruguensis Hook. & Arn. In £. ebano, A. nilotica, and P. lopbantha the spiral is 
counterclockwise, while in P. duke it is clockwise. Though this is true of all shoots 
on the individuals examined, it has not been determined if it is true for the species 
as a whole. Dormer (1954) and Tucker (1963) noted that in the species they studied 
the phyllotactic pattern alternates between orthotropic and plagiotropic shoots. In 
most of the species studied here the distinction between orthotropic and plagiotropic 
shoots is arbitrary, but when two types are distinguishable, the phyllotactic pattern 
remains the same on both. In Lysiloma microphyllum the phyllotaxy on long-shoots 
and vegetative short-shoots is distichous, that of reproductive short-shoots is 
apparently spiral though this interpretation needs confirmation. 
Most of the species exhibit a gradual elongation of the internodes, that is elongation 
takes place more or less continually from the first plastochron. In E. ebano, however, 
elongation of the internode on long-shoots is abrupt and always takes place between 
the seventh and eighth plastochrons. 
The buds, either axillary or terminal, are protected in one of three ways, these are 
comparable to the characters used in the cladistic analysis of Ingeae (Grimes 1995). 
In Paraserianthes lopbantha the leaf-rachis enlarges rapidly, and the apical meristem is 
protected by a series of these enlarged rachises (char. 18, Grimes 1995). In Acacia 
nilotica and Ebenopsis ebano the apical meristem is protected by stipular spines, even 
though the two species differ in the time of inception of the stipules (see below). 
The apical meristem of Ebenopsis is further protected by an enlarged buttress formed by 
the leaf-rachis. In Zapoteca tetragona and Lysiloma microphyllum the apical meristem is 
protected by the enlarged, overlapping, foliaceous stipules. L. microphyllum, furthermore, 
protects the dormant axillary buds by partially surrounding them in the petiole-base. 
In the data set for cladistic analysis (char. 19, Grimes 1995) the buds of these last two 
species were interpreted as preformed (sensu Brown & Sommer 1992). This is incorrect. 
Though the buds appear preformed, there is either no period of dormancy and the 
shoots grow throughout the year, or if there is some dormancy, all the metamers that 
make up the RGU are not already formed within the buds. (Note that this should have 
no effect as the character can be redefined as: buds 0 - not enclosed by stipule-pairs, 
1 - enclosed by stipule pairs). Stein (1975) noted that the stem-apex of Hymenaea courbaril 
is likewise protected by stipule-pairs that cover their associated leaf. He considered this 
to be an unusual condition. 
There are two different types of axillary bud 'systems' in the species examined that 
only partially conform to the definition of primary and secondary bud complexes of 
Halle et al (1978). Primary complexes, or those in which several meristems are 
initiated separately within a single leaf-axil, are known in Acacia nilotica, Zapoteca 
