structure must rely largely on a study of developmental 
and evolutionary variations in the manifestation of the 
phytomers. Discussion of such variations will orient the 
floral expression of the phytomer and, thereby, aid in 
identifying the vestiges of certain reduced parts. 
Leaves. Although the leaf of the vegetative phytomer 
is enlarged for maximum photosynthetic activity, the 
floral homologue is reduced and modified according to 
the protective device characteristic of the species, as well 
as according to the order of the axis on which it is borne. 
At the base of the maize tassel as a whole, or sometimes 
at the base of each tassel branch, the subtending leaf is 
usually reduced (Plate I, D-1), although it may undergo 
all degrees of development (Galinat, 19542). In the ‘‘cen- 
tral spike’’ of the tassel or rachis and corresponding axis 
of the ear, the leaf initials are usually inhibited except 
for a possible rudimentary leaf, the ‘‘glume cushion,”’ 
at the base of the glumes. But this leaf may be well- 
developed in certain bamboos (Holttum, 1956), in Cow 
(where it has a protective role) and in the corn grass and 
teopod mutants of maize (Galinat, 1956). On the spike- 
let axes or rachillas, the blade-parts (laminas) of the first 
two leaves (glumes) are rudimentary, but in the case of 
the third and fourth leaves (lemmas), single genes may 
cause the blades to develop as awns in the ‘‘bearded”’ 
varieties of small grains, or the blades may be stimulated 
to complete development in proliferated spikelets. 
Awvillary buds and internodes. The axillary buds rep- 
resent the starting points for the internodes of new axes 
of lesser orders. Certain variations in their derivatives 
(tillers, ear-shoots, tassel-branches, spikelets, florets) 
demonstrate the homology of the buds concerned and of 
the internodes of their ultimate axes. This is especially 
apparent in the various intergrading branches of the mu- 
tant ‘‘corn grass,’’ which is characterized by a gradual 
[ 6 ] 
