branches during development have been compressed 
around the central spike. Indeed compression is a com- 
mon phenomenon in the grass inflorescence. Its impor- 
tance has been clearly recognized by several students of 
the Gramineae and has been strongly emphasized by 
Arber (2). The Tripsacum inflorescence is of interest, in 
my opinion, not in indicating fusion, but in suggesting 
(as pointed out by Dr. Croizat) how maize ears with odd 
numbers of rows of paired spikelets and rows of grain 
not in multiples of four mzeht have originated through 
fusion. This possibility is illustrated in Fig. 2. Fig. 2a 
_7— Spikelets 
Figure 2. Diagrams showing how fusion of two-ranked branches 
such as those of Tripsacum might give rise to ears with rows of paired 
spikelets in odd numbers. With the development of the abortive spike- 
let, the structure illustrated in diagram A would give rise to a twelve- 
rowed ear. But the condition illustrated in B, because one row of 
spikelets is abnormally oriented and ““buried,’’ would produce a ten- 
rowed ear. 
shows the condition most commonly encountered when 
three branches are brought together to form a cylinder. 
Had an ear of maize originated through the fusion of 
three branches such as these illustrated it would have 
become a twelve-rowed ear for the circumference of the 
axis bears six rows of spikelets which, though solitary 
in Tripsacum, are always paired in maize. 
Fig. 2b illustrates a condition encountered much less 
[ 48 | 
