14 BULLETIN 971, U. S. DEPARTMENT OF AGRICULTURE. 



branches to spikelets first took place on the lateral inflorescences, 

 the terminal inflorescences undergoing alteration later. However, 

 it can not be stated definitely that the reduction of branches of the 

 staminate and pistillate inflorescences is due to completely inde- 

 pendent genetic changes. The fact that the ramose variation as 

 found had both inflorescences much branched and that they remain 

 closely associated in most hybrids is an argument in favor of the 

 hypothesis that the type of branching is constitutional with the 

 plant and not restricted to particular inflorescences. If this were 

 true, the ability to produce a highly ramified pistillate inflorescence 

 on a plant with but little more than a normal number of branches in 

 the staminate inflorescence would be attributed to genetic changes 

 that have taken place since the original suppression of branches. 



In this connection it is of interest to note the experience of Mr. 

 J. M, Mack, of Fall Brook, Calif., who for 11 years has been unsuc- 

 cessfully attempting to eliminate the ramose type of ear from a 

 variety of sweet corn. The ramose variation made its appearance in 



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Fig. 5. — Diagram showing the pedigree of Mack's Yellow Evergreen sweet corn. 

 Classifications marked with an asterisk C*) are based on the ear characteristics ; 

 most of the normal plants had intermediate tassels. 



Mr. Mack's stock in 1909, three years before its discovery by Gernert. 

 Undoubtedly both strains originated independently, though crosses 

 have proved them to be genetically identical. The seed of this sweet 

 corn, used in experiments by the Office of Acclimatization and Adap- 

 tation of Crop Plants, was received from the Office of Seed and Plant 

 Introduction, United States Department of Agriculture, FHB No. 

 23573, in March, 1917. Some of the plants grown from the seed in 

 1918 were found to have typical ramose tassels (PI. XIII), while 

 others showed a well-marked intermediate stage (PI. XIV), the 

 whole progeny with respect to the tassel falling into three fairly dis- 

 tinct groups of 17 normal, 2 intermediates, and 2 ramose. When the 

 ears were harvested it was found that none of the intermediate or 

 normal plants bore branched ears, and only one of the ramose plants 

 bore a branched ear, but this was a typical ramose ear. The ears 

 borne on the plants with intermediate ramose tassels showed no indi- 

 cation of the ramose character, the rows being regular, the pedicels 

 short, and the ears only moderately tapered. The intermediate tas- 

 sels differ from those developed in the Eamosa-Gordo hybrids in that 

 the only trace of Ramosa is the short central spike accompanied by 

 the rather large number of branches (PI. XIV). 



i 



