teosinte (fig. 5), depending upon the degree of depression. 
The extreme depression of the rachis segments in teo- 
sinte and 7'ripsacum seems to require a rigidly erect and 
sessile condition of solitary spikelets in combination with 
a thickened rachis. In the staminate rachis, the spikelets 
are paired, the rachis is more slender and the cupule de- 
velopment is weak or absent. A condition somewhat 
similar to that of the staminate rachis may be produced 
in the pistillate region by introducing the tunicate (7%) 
gene of maize. Thus, in tunicate teosinte, as in tunicate 
maize, the pistillate spikelets become more pedicellate 
and accentuated at the expense of a more slender rachis 
and they are able, thereby, to bend away from the rachis 
sufficiently early to leave little or no depression in it. 
Under such conditions, the would-be cupule lining as- 
sumes many of the aspects of a flattened pulvinus (Plate 
IV, figs. 1, 4). 
The identification of the small bundles from near the 
outer or convex surface of the rachis segments as rind 
bundles is more obvious in the relatives of maize than it 
is in the cupule wings of maize, because the two-ranked 
condition of the former, as compared to the many-ranked 
condition of the latter, simplifies comparison with its 
counterpart in the culm, which is also a two-ranked axis 
(Plate LV, figs. 2, 3, 5, 6). The course of these rind bun- 
dles, as well as those of the stronger inner bundles in all 
members of the American Maydeae, tends to be strictly 
vertical, even though in the cases of teosinte and T'rip- 
sacum, the spikelet positions alternate between opposite 
sides of the rachis. Consequently, in these relatives of 
maize, the small bundles from the wing area of one seg- 
ment extend upwards into a dorsal position in the next 
segment above as they assume a position identical to 
those in the rind of the culm. Finally, in the third seg- 
ment, some of these bundles merge with those from the 
[ 26 ] 
