lay in the fact that in most cases the change from 
branches to spikelet is abrupt. In the tassel there are 
usually only well-defined branches at the base and only 
spikelets on the central spike. In most cases there is no 
transition from branches to spikelets. Collins found some 
evidence of such a transition in varieties of pod corn, but 
the condition in pod corn was by no means as convincing 
as the various transition stages later described and illus- 
trated by Weatherwax (16) in branch (ramosa) maize. 
The studies of Bonnett (8) have a bearing on this prob- 
lem for they show that in the development of the tassel 
there are no discernible differences between the initials 
that become the lateral branches and those which be- 
come differentiated into spikelets. 
The conception of the ear of maize as a spike homolo- 
gous to the central spike of the tassel, and like the latter 
having arisen through the reduction of branches, (a re- 
duction usually completed in the ear, but seldom in the 
tassel) appears to be clear, reasonable and in complete 
harmony with the facts. Weatherwax (16, 19) contends, 
however, that this hypothesis alone is not adequate since 
it does not answer the question of how the polystichous 
condition originated in maize or other grasses. He, there- 
fore, interprets the maize ear in terms of spiral phyllo- 
taxy. The four-rowed ear (like the arrangement of the 
leaves on the stem) is regarded as including a single spiral ; 
the eight-rowed ear includes two spirals, ete. 
Weatherwax has made an important contribution in 
recognizing and describing the spiral phyllotaxy charac- 
teristics of some (probably not of all) maize ears, and in 
showing the resemblance of the maize ear to the spikes 
of other grasses such as Pennisetum. Phyllotaxy, how- 
ever, describes rather than explains the change from the 
distichous condition typical of the grasses in general to 
the polystichous condition characteristic of the inflores- 
[42] 
