MAIZE— KEMPTON 399 



Although wholesale abortion is not a very satisfactory explanation 

 on which to base theories, it cannot be ignored in considering the 

 origin of the ear. Those who reject the fasciation, branch suppression, 

 or yoked spikelet explanation of the origin of the ear are left with the 

 theory that the ear, like Topsy, just developed. 



In the present state of knowledge of the corn plant the idea of the 

 origin of the central spike of the tassel by the suppression of branches 

 offers the most reasonable explanation of this organ, and once given 

 the central spike, the ear can be derived without further controversy. 



Wliat caused the suppression of the branches of the tassel, if in fact 

 that is what happened, and what species of grass had the branches 

 suppressed is an entirely separate problem. Nor is there any solution 

 of why in maize both members of the paired female spikelets develop 

 while in all other members of the tribe one member of each pair is 

 suppressed. Here, too, there are several theories. One school of 

 thought has corn derived from teosinte by gradual evolution aided in 

 its later stages by man. AlHed to this explanation is the suggestion 

 that maize originated from teosinte by mutation or a series of muta- 

 tions. The essential difference between origin by mutation and origin 

 by evolution and selection is one of the magnitude of the stages. 

 If the mutations were many and of small effect there is no difference 

 between the two, but if maize sprang fullfledged as a single mutation 

 from teosinte the two theories are quite divergent. A second group 

 holds that com and teosinte developed from a plant something like 

 gama grass, the two genera splitting off from this common stem. 

 The proponents of this theory hold that the line which developed into 

 maize consisted of plants more maizeUke than teosinte but still able 

 to survive as wild plants. Their usefulness to man stimulated selec- 

 tion, and eventually the wild plants disappeared presumably to con- 

 found the students of maize. A third suggestion has been made that 

 maize has been developed from a chance hybrid of teosinte and some 

 other grass not specified but indicated as probably belonging to the 

 sorghum tribe. Each of these theories has merit though none offers 

 a satisfactory explanation of all the facts. 



The floral unit of the grass family is the spikelet, and in the tribe of 

 which maize is a member, the male spikelets are borne in pairs, one 

 stalked, or pediceled, the other without a stalk, or sessile, each spike- 

 let containing two flowers. The female spikelets of all the maize 

 relatives are borne singly and are one-flowered — one whole spikelet 

 and one flower having been suppressed, but in maize the female 

 spikelets are stiU paired, though normally each develops but a single 

 flower, which explains why the number of rows of kernels on an ear 

 are found in multiples of two. 



The seeds of most kinds of maize are naked, the glumes of the fe- 

 male spikelets having become greatly reduced in size and membrana- 



