Arrangement of Spikelets. Another important 
difference in the two types may lie in the arrangement 
of the sessile and pediceled spikelets on the ear. If the 
ear of maize is a spike only recently derived from a pan- 
icle by reduction of branches then the arrangement of the 
paired spikelets with respect to the position of the pedi- 
celed and sessile member of each pair should be largely 
a random one because the branches of the panicle are 
arranged at random with respect to the position of the 
pediceled and sessile spikelet of the lowest pair. If, how- 
ever, the ear has come under the influence of Tripsacum 
genes to the extent that it behaves as a structure de- 
rived from the distichous spike of teosinte, then the ar- 
rangement of the spikelets may well be a systematic one. 
Unless I have inadvertently overlooked a reference to 
it in the literature, the question of the arrangement of 
sessile and pediceled spikelets on the ear seems never to 
have been answered. Collins (5),assuming that it is always 
pediceled spikelets which abort when rows of grain are 
dropped between the base and tip of the ear, asserted 
that he had never seen an instance where the dropped 
rows were either adjacent or separated by two rows. This 
he regarded as evidence that the arrangement of pedi- 
celed and sessile spikelets around the circumference of 
the ear is not the one expected from the fusion of two- 
ranked spikes. He apparently concluded, although he 
certainly did not prove, that the arrangement is, instead, 
the one that would be expected if the ear had resulted 
from yoking and twisting in the distichous spike. 
Actually, since all pistillate spikelets are sessile (al- 
though one member of each pair is potentially pediceled) 
it is impossible to determine from the external appearance 
of the ear the nature of the arrangement of its spikelets. 
But since the central spike of the tassel is clearly the 
homologue of the ear, and since on the central spike the 
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