scribed in the ear (pistillate rachis) and in the tassel 
(staminate rachis) by Reeves (1946, 1949) and Lauben- 
gayer (1948, 1949); in the tassel alone by Kumazawa 
(1939); and in the culm (stalk) by Esau (1943) and 
others. Certain bundles in the ear have been suggested 
as representing those of a lateral organ (the prophyll) 
which is fused to the main axis or rachis (Nickerson, 
1954). These previous studies are largely descriptive, 
interpretations being difficult because the tissues and 
vascularization in maize was not compared with those of 
its close relatives; nor was the anatomy of the rachis con- 
sidered as a possible reflection of the structure of the 
culm. The present study attempts to examine the evo- 
lution and development of the maize plant in terms of 
modifications, according to function, of the organs in a 
single basic pattern, the phytomer. 
In addition to typical maize (sweet corn inbred Purdue 
39) and its relatives, teosinte (race Durango) and T'rip- 
sacum dactyloides, two special maize-ty pes were included 
in this study. One of these is a derivative from a maize- 
teosinte hybrid specifically bred for a simplified version 
of the vascular system which could be represented in 
three dimensions. ‘This breeding was done by selecting 
a slender, four-ranked ear with greatly accentuated cu- 
pules’ which were free from the usual crowding and 
distortion. Reduced condensation to remove vertical 
compression between the cupules was derived from Gua- 
rany maize. Enlargement of the lateral wings of the cu- 
pules, a character associated with spikelets oriented in 
the same plane as that of the rachis (Galinat, 1956), was 
introduced from teosinte. Pairing of the spikelets, a 
characteristic of maize, further accentuated the cupules 
by spreading out the lateral wings. The other special 
2 Corneous alveoli of the maize cob immediately above the attach- 
ment point of each pair of pistillate spikelets (Sturtevant, 1899). 
[ 2 | 
