in 7. australe suggests that in South America, as in Cen- 
tral and North America, Zea contamination has probably 
increased the variability of Tripsacum. The most obvious 
effects of the Tripsacoid tendency are compression and 
condensation, with hardening of the parts, straightening 
of rows, reduction in row number, shortening of pedicels 
and sinking of parts into pits or alveoli on the rachis. 
Tripsacum, Zea and related grasses probably had some 
common ancestor and it is usually impossible to decide 
definitely how some particular variation might have been 
introduced. 
The term ‘‘Andropogonoid”’ is not meant to suggest 
that this tendency is derived directly from the genus 
Andropogon or even from the family of this name, but 
the effect is so reminiscent of some Andropogons that it 
is well to keep the similarity in mind. The Andropogon- 
oid tendency is toward freely branched parts, long ped- 
icels and fibrous, as opposed to brittle parts. 
A type of fasciation in which there is shortening of 
the longitudinal axis with continued development of the 
parts probably plays a much greater role in maize than 
is usually admitted. The origin of the ear as a fasciation 
was suggested long ago, but received little serious con- 
sideration. Recently, Anderson (1944) suggested that 
Mexican Pyramidal maize is fasciated. Fasciations occur 
frequently in other wild and cultivated plants (White 
1945). A familiar example is cockscomb, which is rarely 
seen except as a fasciated plant. Oca, an oxalis cultivated 
in the Andes and parts of Mexico, produces its best ed- 
ible rhizomes on plants with fasciated stems. The ear-like 
structure of 'Trichachne is probably a fasciation. Fascia- 
tions may be produced by the environment or be heredi- 
tary (although some of the hereditary ones appear only 
under certain conditions), and probably possess modi- 
fiers. If a primitive maize was a fasciation, it would have 
[ 264 | 
