segments’’ are closed by the outer glumes of the enclosed 
spikelets. he spikelets, which are sessile and solitary, 
are oriented in the same plane as that of the rachis and 
are sunken within the cavity. 
The inflorescences of these close relatives of maize have 
slight differences which will be considered in terms of the 
hypothesis that teosinte originated from the ancient hy- 
bridization of maize and TJ'’ripsacum (Mangelsdorf and 
Reeves, 1939). Furthermore, we assume that the maize 
germplasm in teosinte is now rather similar to that of 
modern maize, since teosinte is being frequently out- 
crossed to maize. Extreme compression’ of the pistillate 
spike and its shank (a peduncle including an entire 
branch) is an outstanding feature of domesticated maize 
(Weatherwax, 1935; Mangelsdorf, 1945). The inter- 
nodes of the shank are so short that all of the leaf-sheaths 
(husks) remain in a protective cover upon the mature 
ear. Increased compression which was derived from 
modern maize is thought to have produced the fruit case 
and peduncle of teosinte by modifying the characteristics 
of Tripsacum as follows. Compression of the trapezoidal 
or almost rectangular form of the rachis-segment of J'rip- 
sacum has produced the triangular shape characteristic of 
the rachis-segment in the most maize-like races of teo- 
sinte. The elongated peduncle in 7’ripsacum usually holds 
the mixed inflorescences aloft above all leaves, and conti- 
nuity of the pistillate region is maintained during matu- 
ration by masses of parenchyma which connect adjoining 
rachis-segments. <A slight compression produces the 
teosinte-type of peduncle in which a subtending spathe 
remains about the maturing pistillate spike and, thereby, 
provides support in lieu of nodal parenchyma. 
The features of the hollow rachis-segments of teosinte 
1 ‘ : ‘ - P . 
This type of longitudinal compression is sometimes referred to as 
condensation or telescoping. 
[ 219 ] 
