to ashorter, coriaceous structure marked by various types 
of sculpturing (Manisuris spp. ; Hackelochloa spp.) and, 
finally, to a highly lignified glume which is specialized in 
shape, texture and plane of divergence so as to bring 
about the closure of the narrow opening of a lignified 
prophyll which is adnate to a depressed rachis-segment. 
Various inherent modifications of this glume also occur 
in maize (Galinat, in press). In normal maize, it may be 
coriaceous in texture (many South American varieties) 
or, more commonly, it may resemble its counterpart in 
teosinte in being corneous or indurate (teosinte contam- 
inated varieties from North and Central America). 
PARALLEL EvoLurion IN THE Hordeae 
The Hordeae series. The combination of a compact 
spike and a continuous rachis is rather frequent in the 
agriculturally important tribe, Hordeae. Here the spike- 
lets are borne singly, although they are perfect and usu- 
ally multiflowered. Occasional reductions within the 
spikelet and a thickening of the rachis have produced a 
parallel series leading to the formation of something ap- 
proaching the cupulate fruit case. An outstanding differ- 
ence between these series lies in the nature of the outer 
glume which closes the cavity in the rachis. In the An- 
dropogoneae and Maydeae, the enclosure is completed 
by the first glume; while in the Hordeae (Lolium and 
Monerma), the spikelet is placed in the opposite direction 
so that the second glume is outermost. 
Of the five successive stages representing the Hordeae 
series (Plate LVII, figs. 1-5), only the end result (MWon- 
erma cylindrica) has progressed beyond a type suitable 
for culture as a grain plant. T'wo of the other genera 
(A gropyron spp. and Aegilops spp.) are thought to have 
contributed directly to the evolution of the genus T'rit- 
cum and so to the development of the bread wheats. 
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