the ears, but no attempt was made to distinguish them on 
the basis of differences in their basic structures beyond 
pointing out that many of the Andean varieties (presum- 
ably ‘‘pure’’ maize) are characterized by irregular rows 
of grain, while many Central and North American va- 
rieties (presumably contaminated by 'Tripsacum) exhibit 
straight rows frequently separated in pairs. Extreme 
types approaching these descriptions were found by Man- 
gelsdorf and Cameron (12) in a study of maize varieties 
of western Guatemala and are illustrated in their paper. 
Now the evidence that there are two kinds of maize 
ears basically different in origin, structure and phyllo- 
taxy, if not conclusive, is at least highly convincing. 
The first type of ear which is characteristic of the 
Guarany pod corn and is probably typical of ‘‘pure”’ 
maize may be described as a compacted spike with pairs 
of pistillate spikelets borne in varying numbers at the 
nodes of a simple, weakly articulate rachis. The ear has 
a whorled phyllotaxy but may assume, more or less for- 
tuitously, especially if the rows and kernels are crowded, 
the aspect of spiral phyllotaxy. The rows may _ be 
straight, especially if the row number is low; but straight 
rows like spiral phyllotaxy seem to be, as they are in cer- 
tain other grass spikes, fortuitous rather than the reflec- 
tion of a particular kind of underlying structure. Straight 
rows, in some cases at least, seem to represent nothing 
more than an efficient arrangement assumed upon crowd- 
ing. Pairs of rows are not distinctly separated and if 
there is sometimes an apparent line of demarcation be- 
tween pairs of rows it separates the two spikelets of the 
same pair and not two pairs of spikelets. ‘The number 
of rows is a reflection of the degree of compaction rather 
than of the complexity of the phyllotaxy for the number 
of rows can change decidedly from base to tip without 
any change in the underlying phyllotaxy. With respect 
[ 68 ] 
