8 BULLETIN" 925. U. S. DEPARTMENT OF AGEICCLTTKE. 
MORPHOLOGICAL SIGNIFICANCE. 
The recurrence of brachysm in maize is perhaps to be understood 
from the normal presence of this characteristic in both staminate 
and pistillate inflorescences. In cotton it appears as a lack of differ- 
entiation between the floral parts and the internodes of the fruiting 
branches, and not only are the internodes reduced but the floral bracts 
are modified, becoming leaflike while the leaves become bractlike (4) . 
In maize, however, there is no indication of changes on the main 
culm other than the shortened internodes. and the leaves are normal. 
The most striking example of brachysm in maize is the normal 
pistillate inflorescence. Here a lateral branch has suffered so exten- 
sive a reduction in the length of the internodes that even the 
lower leaf sheaths of the branch inclose the terminal inflorescence. 
In this respect the brachysm of the pistillate inflorescence resembles 
that found in cotton, since the leaf blades have become much re- 
duced or more frequently lost and only the sheath remains. This 
is an approach to the floral condition where the glumes of the 
spikelets are homologous with the leaf sheaths, and in this respect 
the brachysm may be said to represent an intermediate condition 
between floral and vegetative parts belonging to that class of varia- 
tions designated by Cook (4) as metaphanic. This brachytic ten- 
dency is usually confined to the branches from the upper nodes, 
while those produced at nodes near but not necessarily below the 
surface of the ground have internodes of normal length. In some- 
tropical varieties of maize the brachytic specialization of the upper 
branches has been lost, and the result is a grotesque plant with one 
or two ears borne at the ends of enormously lengthened ear stalks 
which frequently exceed the main culm in height (PL ATT). 
When accidents force into growth the branches below the ear. which 
ordinarily remain dormant, they increase in length, or. in other words, 
reduce in specialization, progressing toward the base of the plant. 
The place where these branches change from having pistillate to 
staminate terminal inflorescences is usually marked by a more com- 
plete abortion of the buds, leaving an unbranched section of two or 
three internodes. Thus the brachysm of the lateral branches is an 
excellent illustration of a graded specialization, indicating gradual 
development, but. although there are all stages of branch brachysm 
on an individual plant, the advanced stages, as found on ear stalks, 
are little affected by environment. 
Euchlaena. the nearest relative of maize, has no such specialization. 
and. although all of the nodes except the uppermost produce a branch, 
the apices of these branches are usually about the same height from 
the ground. This results from the fact that in progressing toward the 
apex of the plant each succeeding branch has one less node than the 
