formation of asingle large spike, the ear; but in teosinte, 
where the individual spikes are small, there is sufficient 
energy for the development of clusters of spikes. 
DiscusslION AND SUMMARY 
The structure of the entire plant of maize and its rela- 
tives results from various controlled manifestations of a 
basic pattern of organs, the phytomer. The parts of the 
phytomer have been recognized in vegetative form as an 
internode, a leaf, an axillary bud and a prophyll. These 
organs, as well as their organization in the phytomer, 
constitute specialized regions without exact boundaries. 
Nevertheless, the phytomer represents a fundamental 
design which occurs repetitiously throughout the entire 
plant. A comparison of its various manifestations is sim- 
plified, if we select a cycle comprising the group of organs 
which are adjacent to a given node rather than to use the 
classical delimitation which includes lateral organs at 
opposite ends of a given internode. 
The reduction of parts of the phytomers which have 
internodes along the rachis is usually extreme. Tor ex- 
ample, the leaves which potentially subtend the spikelets 
are usually reduced to glume cushions or swellings at the 
base of the glumes, although certain genes (7p, Cg) may 
stimulate their development as typical leaves. ‘These 
glume cushions are vascularized by small-bundles which 
might be regarded as rind-bundles rather than the vascu- 
lar remains of rudimentary leaves, because they connect 
with the vascular supply to the outer glumes rather than 
terminating as stubs. More information is needed con- 
cerning vascularization of swellings associated with un- 
successful attempts at leaf development. 
The prophyll is another phytomeric part which is 
highly reduced along the rachis. In the staminate rachis 
at the axils of tassel branches, it assumes the functional 
[ 28 J 
