6 kempton: ancestry of maize 



leading. There is and can be no question that Zea, Kuchlaena, 

 and Tripsacum have a common ancestry, but whether the 

 differences between Zea and the other genera can be more satis- 

 factorily explained by ascribing the diversities to simple evolu- 

 tion from a single common ancestor than by assuming a hybrid 

 origin is a question that to the writer's mind has not been fully 

 appreciated by Weatherwax. To answer these questions, 

 differences must be considered, as well as similarities. 



One of the chief differences between Zea and the other genera 

 lies in the form of the pistillate inflorescence, or ear, the origin 

 of which has been the subject of much discussion. The theory 

 receiving the greatest support is that of fasciation, proposed by 

 HackeP and accepted by Gernert,^ Worsdell,'' and others. This 

 theory is open to the objection that it fails to account for the 

 fact pointed out by Mrs. Kellerman^ and Montgomery,'^ that the 

 ear is the homologue of the central spike of the tassel. Collins^ 

 has called attention to the fact that the central spike is as much 

 in need of explanation as the ear, and has suggested an alter- 

 native theory, which has been adopted by Weatherwax, that the 

 central spike originated by the shortening of some of the branches 

 of the panicle until they were reduced to paired spikelets. On 

 this basis the ear is homologous with the central spike, the re- 

 duction of the branches having occurred before the male and 

 female inflorescences were differentiated. 



While the latter theory would seem to fulfill the conditions, 

 the case for fasciation cannot be peremptorily dismissed without 

 some explanation of the frequent occurrence of bifurcated ears 

 which breed true. Further support of the fasciation theory 

 is to be found also in a true-breeding race having fasciated and 

 bifurcated central spikes, which we have succeeded in isolating. 

 The full description of this mutation will be published shortly. 



^ Hacked, E. Gramineae. Engl. & Prantl, Nat. Pflanzenfam. 2: 1-97. 1889. 



* Gernert, W. B. Analysis of characters in corn and their behavior in trans- 

 mission. Champaign, 111. 1912. 



* WoRSDELL, W. C. The principles of plant teratology, Vol. 2. London. 1916. 



* Kellerman, Mrs. W. A. Primitive corn. Meehan's Monthly 5: 44. 1895. 



^ Montgomery, E. G. What is an ear of corn? Pop. Sci. Mo. 68: 55-62, figs. 

 1-14. 1906. 

 « Op. cit. 



