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Telopea Vol. 6(4): 1996 
tetragona, Paraserianthes lophantha, Lysiloma microphylliim and Pithecellobium duke; in 
these cases all are biserial or triserial bud systems, as is common in other legumes 
(Dormer 1954; Martinez 1975). At any given node axillary buds are produced in a 
zig-zag fashion by a meristematic region in the axil; maturation is basipetal. The 
buds are actually short-shoots with two or three nodes. In most of the species these 
buds remain undeveloped, but in Acacia niloHca most of them develop proleptically 
as long-shoots. At any given node, the meristematic region in the axil is capable of 
giving rise to other buds. No matter how many buds are formed, however, the 
meristematic region remains in the axil. Cremer (1972) calls this an axillary meristem. 
In contrast, the bud of Ebetwpsis ebano develops as a short-shoot with the same 
phyUotaxy as the long-shoot, but with internodes that do not elongate. In contrast to 
the serial bud system, no other bud has ever been observed to form at a node in this 
species. The meristematic region remains at the apex of the shoot in £. ebano, rather 
than in the leaf-axil as in the other species. This type of bud system is not 
accommodated in the definitions of Halle et al. (1978). 
Pithecellobium duke and Paraserianthes lophantha clearly have two kinds of buds; 
multiple serial buds that evidently produce all vegetative branching, and primary 
buds that develop directly into inflorescences. In P. lophantha these two types are 
more or less separated: the vegetative ones occur on older metamers of any RGU, 
the reproductive ones on younger. Zapoteca tetragona is probably much like 
P. lophantha. In P. duke, however, there is evidently some mixing of the two types of 
buds at some nodes. Lysiloma microphyllum clearly only has one type of bud, which 
develops into a short-shoot on which inflorescences can form, and from which 
long-shoots can develop. Likewise Ebenopsis ebano has but one kind of primary bud 
that develops into a short-shoot. 
In Acacia nilotica a leaf will often form on one of the buds with no shoot-elongation, 
and it then appears that a short-shoot has formed. However, there is no continued 
development of nodes with suppressed internodes. If the apex does become 
meristematic, the product is always a long-shoot. The characters used in the cladistic 
analysis do not adequately reflect these differences (chars. 7 & 8, Grimes 1995). 
While the Acacia nilotica -type of short-shoot and the Ebenopsis ebano -type are both 
branch systems with suppressed internodes, their development is not the same. 
There is a difference in time of origin of the stipules in the species examined. In 
Ebenopsis ebano, Lysiloma microphyllum and Calliandra surinamensis the stipules arise 
directly on the apex simultaneously with, but apparently independent of, the 
leaf-primordium. In Acacia nilotica, Paraserianthes lophantha, and Pithecellobium duke 
the stipules arise on the flank of the leaf-primordium. Assuming that the stipules in 
all these species are homologous, this difference is heterochronic: the stipules of 
E. ebano, L. microphyllum and C. surinamensis arise sooner than in the other three 
species. They also arise apparently spatially independent of the leaf-primordium 
directly from the apical meristem; it appears that their placement relative to the 
leaf-primordium has been changed. In this instance then heterotopy might be a 
result of a heterochronic change. 
Heterotopy has not been studied to the same degree as homeosis. It has been studied 
in the context of epiphyllous inflorescences (e.g., Dickison 1978; Dickison & Saltier 
1974; Saltier 1975a), roots (Yamashita 1970,1972), and leaves (Saltier & Maier 1977). 
Saltier (1975b) provided a generalized discussion, and later (1978) examined 
heterotopy in the context of fusion and floral morphology. In none of these works is 
the relationship between heterotopy and heterochrony mentioned, though the idea 
that homeosis is a result of heterochronic change is becoming widely accepted 
(cf. Coen 1991; Hill & Lord 1989; Lord 1991; Lyndon 1994). As the taxa studied here 
are widely distributed on the published cladogram (Grimes 1995), little may be said 
