62 POPULAR SCIENCE MONTHLY 



a pistillate spike, we have an eight to twenty-two-rowed ear. This 

 accounts for the well-known fact that corn ears are even rowed. 



My observations suggest to me that corn and teosinte may have had 

 a common origin, and that in the process of evolution the cluster of 

 pistillate spikes in teosinte were developed from the lateral branches 

 of a tassel-like structure, while the corn ear developed from the central 

 spike. It is probable that the progenitor of these plants was a large 

 much-branched grass, each branch being terminated by a tassel-like 

 structure, bearing hermaphrodite flowers. Fig. 13 is a diagram of 

 such a plant. As evolution progressed, the central tassel came to 

 produce only staminate flowers, these being higher and in a better posi- 

 tion to fertilize the flowers on the lower branches. At the same time, 

 the lateral branches came to produce only pistillate flowers, their posi- 

 tion not being favorable as pollen producers, while, on the contrary, 

 they were favorably placed to receive pollen. This differentiation in 

 the flowers was accompanied by a shortening of the internodes of the 

 lateral branches until they were entirely enclosed in the leaf sheaths, 

 as shown in Fig. 1. 



Fig. 14 is a sketch of the stalk and ears of a well-developed sweet 

 corn plant after the removal of the leaves and leaf sheaths. It will be 

 noted that the number of nodes in the ear-bearing branches agrees 

 exactly with the number of nodes found in the stalk, above the point 

 of attachment. If these branches were elongated to their normal 

 length, we should have something similar to the diagram in Fig. 13. 

 The lowermost branches usually arise at or below the surface of the 

 soil. They develop their own root systems where they are in contact 

 with the soil, and soon separate from the main plant and become inde- 

 pendent plants bearing a proper tassel and ear, in all respects similar 

 to the parent plant. Intermediate between the tassel-bearing branches 

 and the first ear-bearing branches on the main stem there often may 

 be found one or more branches, the tendencies of which seem to be about 

 equally divided between ear-bearing and tassel-bearing, resulting in a 

 structure combining the characteristics of both tassel and ear. 4 



4 1 wish to acknowledge indebtedness to Dr. Charles E. Bessey for helpful 

 advice during the course of this investigation. 



