152 



The Journal of Heredity 



high temperatures. Peru contributes 

 the largest seeds. From China comes 

 a variety with a new type of endosperm 

 and the abiHty to withstand hot dry 

 winds at the time of flowering. Our best 

 protected ears come from Guatemala. 



Enough has now been said to indicate 

 what is meant by adaptation and how 

 the varieties must be studied to realize 

 and appreciate the adaptations. Only 

 a beginning has been made. When it is 

 realized that no two regions present 

 exactly the same environment and that 

 maize, though a very ancient crop, is 

 very ])lastic and has molded itself to the 

 conditions under which it has been 

 grown, some idea may be gained of the 

 multitude of adaptations that await 

 discovery. 



RIi:t"O.MBINATIOi\ OF CHARACTERS 



A word must now be said regarding 

 the recombination of these adaptations 

 into new varieties suited to new condi- 

 tions or representing an improvement 

 over varieties already existing. 



Regarding the recombination of char- 

 acters, our knowledge is still very im- 

 perfect, but here also a beginning has 

 been made and results sufficient to serve 

 as demonstrations have been secvired. 

 An exam])le may be taken that is 

 particularly a])])licaljlc to tro])ical 

 America. 



When a traveler from the north \-isits 

 tropical America and finds maize a 

 staple crop and often growing lux- 

 uriantly, he is naturally struck by the 

 absence of table or sweet varieties so 

 generally grown in this country. I have 

 made incjuiry in a number of instances 

 and almost invariably have been told 

 that sweet varieties have been intro- 

 duced, but that they did not do well, 

 and that their growth was given up on 

 that account. If it were possible to 

 combine the palatability of the sweet 

 varieties with the luxuriant growth and 

 freedom from insect attack of the natix'e 

 varieties, a valuable addition might be 

 made to the rather meager list of really 

 delicious vegetables available in many 

 parts of the tropics. We are to some 

 extent confronted with the same prob- 

 lem in our own southern states where 

 the ravages of the corn woim j)racticall\- 



preclude the growing of commercial 

 \-arieties of sweet corn. 



In the breeding of commercial varieties 

 of sweet corn, one of the most im- 

 portant considerations has been earli- 

 ness. In breeding for earliness the 

 number of leaves has been reduced. 

 In reducing the niunber of leaves the 

 number of husks, which are homologous 

 to leaves, have also been reduced with 

 the result that the ears of sweet corn are 

 poorly protected. This was of little or 

 no importance north of the region in- 

 fested by the corn worm, but it is this 

 that renders the commercial sweet 

 varieties unsuited to southern regions. 



In 1912 crosses were made between 

 commercial sweet varieties and southern 

 varieties of field corn having well pro- 

 tected ears. The first generation plants 

 were grown in 1913, and selections were 

 made from those plants with the most 

 perfectly protected ears. From the 

 ears thus obtained, which contained a 

 mixture of sweet and non-sweet seed, 

 we selected the sweet seed for planting 

 in 1914. In that season the plants were 

 \'ery variable, but all the seeds were 

 sweet. Crosses were made between the 

 most promising plants, special attention 

 being again paid to the covering of the 

 ears. The results of the past season 

 demonstrated that we already have a 

 fairl}^ uniform and productive variety 

 of sweet corn. Although grown in a 

 region where the infestation of corn 

 worms is ]5articularly severe the dam- 

 age to the ears was insignificant, less, in 

 fact, than was the damage done to field 

 varieties in the same region. Thus in 

 three years we have combined the sweet 

 seeds of the table varieties with well- 

 l^rotected ears of the larger field \'arie- 

 ties. It would appear that there is 

 no valid reason why any region that 

 can grow maize successfully should l)e 

 without sweet varieties. Whether earli- 

 ness must necessarily be sacrificed, or 

 whether it is possible to secure earliness 

 and still keep the wcll-iirotected ears, 

 is an interesting question that must 

 await further investigation. 



All characteristics cannot be manip- 

 ulated as easily as the sweet endo- 

 spenn, which from the alternative 

 nature of its inheritance pennits of 



