in being corneous or indurate (in teosinte-contaminated 
varieties from North and Central America). The degree 
of this induration has been used as an estimate of teosinte- 
introgression in archaeological maize, after the reliability 
of the method has been established (Galinat et a/, 1956). 
Internally, the mesophyll of the glume is divided into 
definite specialized regions. The induration is confined 
to a region of smaller cells extending from the outer epi- 
dermis to a line delimited by a row of vascular bundles 
about midway through a cross section (Plate X, fig. 8). 
As indicated by strong safranin staining, these smaller 
indurated cells are characterized by an accumulation of 
lignin in the secondary walls. The remainder of the 
glume, extending to the inner epidermis, consists of large 
parenchyma-cells. During final maturation of the glume, 
this parenchymatous tissue collapses from desiccation. 
The resulting shrinkage of the parenchyma toward the 
bundles causes an outline of the vascular system to be 
revealed as parallel ridges along the inner epidermis. 
The vascular arrangement of the normal glume differs 
slightly from that which occurs in a vegetative leaf- 
sheath. The glume has smaller bundles and, since this 
organ is determinative, they converge at the apex. In 
the leaf-sheath these principal bundles remain parallel as 
they continue on into the blade. As in the leaf-sheath, 
the parallel bundles are of two sizes with the larger ones 
alternating with one or two smaller ones. ‘The small cross 
connections which anastomose between the parallel bun- 
dles are confined to the apical region of the glume as 
compared to a distribution along the entire length of 
both the blade and sheath of the leat. The glume wings 
are non-vascular as are the ligules and sheath-auricles of 
the leaf-sheath. It seems that these vascular differences 
between glumes and leaf-sheaths are more in the nature 
of minor modifications. 
[ 59 | 
