Grimes, Mimosoid legumes 
731 
phylogenetic hypothesis. Homeosis is 'the assumption by one part [of an organism] 
of likeness to another part', or 'the complete or partial replacement of one structure 
with a different structure.' Heterotopy is the change in the position of inception of 
organs (Sattler 1978). Several authors argue that homeosis is a special case of 
heterochrony (Coen 1991; Hill & Lord 1989; Lord 1991; Lyndon 1994), and Lyndon 
(1994) points out that while homeotic genes are often assumed to be positional 
genes, their role in regulating timing (heterochrony) should be distinguished from 
any role in affecting position. The role of heterochrony in affecting or effecting 
heterotopic changes remains unstudied, and the relationships between heterochrony, 
heterotopy and homeosis require theoretical discussion. 
Martinez (1975) published a study of axillary buds but did not include developmental 
studies. She included two species of Ingeae, Inga uruguensis Hook. & Arn. and 
Pitlwcdlobiian grisebachianum (= Chloroleucon foliolosum (Benth.) G. P. Lewis), and two 
species of Acacieae, Acacia caven (Mol.) Mol. and A. visco Lor. ex Griseb. In that 
paper three types of axillary bud-systems were found: solitary, multiple serial, and 
multiple biserial. Multiple serial buds are aligned in one series along the axis of the 
stem; multiple biserial buds occur in a zig-zag or alternate fashion in two series 
along the axis of the stem. Martinez noted that in all cases maturation of the buds 
was basipetal, but did not note any differences in timing of maturation of the buds 
relative to other organ-systems. Individual taxa included in this work will be 
discussed further and comparisons made below. Chloroleucon foliolosum is quite 
different in that the buds are apparently preformed and enclosed in perules. Origin 
of unit-inflorescences and heterochronic differences in formation of leaves and 
unit-inflorescences were not mentioned. Branch and inflorescence development in 
the two species of Acacia is apparently quite similar to Acacia nilotica, discussed 
below. The condition in Inga uruguensis is similar to many discussed herein but, 
without notes on heterochronic phenomena and developmental studies, more specific 
comparisons are not possible. 
Materials and methods 
The taxa chosen for study were those for which living material was available either 
from nurseries, or in cultivation by the author or at the New York Botanical Garden. 
The taxa studied are: Paraserianthes lophantha (Willd.) I. Nielsen, Zapoteca tetragona 
(Willd.) H. Hern., Lysiloma microphyllum Benth., Acacia nilotica (L.) Willd., Ebenopsis 
ebano (Berlandier) Barneby & Grimes, ined., and Pithecellobium duke (Roxb.) Benth. 
Buds were dissected fresh and fixed (or fixed and then dissected) for 24-48 hours in 
FPA (formalin:proprionic acid:95% EtOH:water, 5:5:45:45) and stored in 95% EtOH. 
Dissection was done on a Wild M5 dissecting scope. Specimens were taken through 
a dehydration series to 100% acetone, critical point dried on a Denton DCP-1 
apparatus, coated in a Hummer sputter coater with gold-palladium, and examined 
at 2 or 5 kv on a JEOL JSM-T300 scanning electron microscope. 
Results 
Paraserianthes lophantha (Willd.) 1. Nielsen (Figs 1, 2a-d, 3a) 
Paraserianthes lophantha is native to the East Indies and south-western Australia. The 
typical subspecies is widely cultivated, and naturalized in the San Francisco Bay 
area of California. Observations were made one time on a population in San Francisco, 
and on plants grown from seed from that population cultivated over two years. 
