are now found or which may in prehistoric times have 
been introduced from another region. The study of pre- 
historic maize must be based largely upon the ears, for 
even where other material is found, it is practically never 
associated with an ear. For this reason a special set of 
characters must be utilized. ‘The most useful ones are in 
the glumes and alveoles of the ear, but before valuable 
prehistoric material can be studied with maximum pro- 
fit, a technique must be developed which will not destroy 
the specimens being studied. 
Thickness of cob varies greatly and is quite indepen- 
dent of the number of rows of grains. The cob may be 
fibrous and flexible or lignified, hard and stiff. The paired 
female spikelets may be attached by a broad base to the 
lower margin of the alveolus so that a definite line of sep- 
aration between glumes and cob is lacking, or the spike- 
lets may be borne on a pedestal as much as 2 mm. tall. 
Glumes vary from horny, thickened and sculptured 
masses to delicate membranes, although the variation 
within each race is rarely very great. Lemmas and paleas 
vary much less. 
Grains range from bird-shot sized spheres through 
pointed, beaked, polygonal, dented and other forms to 
the broad Cuzco grain. Most difficult to interpret is the 
occurrence of denting, and until some information on the 
cause and control of denting is available, it is impossible 
to discuss the distribution intelligently. Denting is found 
occasionally in all the races although it is often so slight 
as to be barely perceptible. It is strongly present in 
some Valle and Cuzco maize. 
Isodiametrical polygonal grains which are widest at 
their tips are usually correlated with tesselation. This 
arrangement and shape of the grain is characteristic of 
Coroico and Guarani maize, which might lead one to sus- 
pect that they have been contaminated with Tripsacum, 
[ 276 | 
