phytomers of the rachis. ''wo independent theories have 
been proposed for the role of the prophyll in the devel- 
opment of the ear and tassel of maize. Nickerson (1954) 
suggested that the cupule in the ear was formed by a 
prophyll depressed into and adnate to the rachis, except 
for the auricles which produce laterally as ‘‘rachis-flaps. *’ 
In the tassel of maize, which lacks cupules, as well as in 
the paniculate rachises of other grasses, the primordial 
prophyll may have been contained as an axillary swelling 
(the pulvinus) which has become specialized to function 
in spreading the primary branches at the time of anthe- 
sis (Galinat, 1956). Arber (1934) has noted that the in- 
florescence branches of many grasses have such axillary 
pulvini, which expand at the time of anthesis so as to 
force the branches outwards; and, after anthesis, the 
swellings usually wilt as the branches again rise. 
INTERNAL ANATOMY AND MANIFESTATION 
OF THE PHY'TOMER 
Although the homologies of certain reduced and mod- 
ified organs in the floral phytomer may not be apparent 
externally, their basic nature may lie hidden in some 
part of the internal anatomy, such as that of the vascu- 
lar system. An anatomical study, therefore, may help to 
establish the anatomical remains of the prophyll at certain 
of its potential positions which are occupied by other 
excrescences, such as the cupule in the ear and the pul- 
vinus in the tassel. 
Vascularization in maize. The homology of the floral 
and vegetative internodes is reflected by a close similar- 
ity in their vascular systems. Certain modifications in 
vascularization of the ear are caused by the reduction and 
compaction of lateral organs. Since vascularization in 
the tassel is so similar to that of the culm (Kumazawa, 
1939), it will be excluded, except in regard to the pul- 
[8] 
