148 



The Journal of Heredity 



varieties of corn, I shall enumerate a 

 few of the more striking adaptations 

 that have thus far been discovered, 

 bej^'inninj,' with the varieties grown by 

 the Indians of the western United States. 



HOI'I .MAIZH 



The Hoj^i, Xavajo, and Zuiii Indians 

 are still growing a type of maize that 

 seems to ha\'e sijread but little outside 

 the region inhabited by these tribes. 

 The ]3revailing type of seed is soft or 

 amylaceous, the jjlants tiller abundant 1 \-, 

 the>- are earh' maturing, and make com- 

 parative! >' rapid growth at low tempera- 

 tures. Their exact water requirement 

 has not been determined, 1)ut it would 

 appear that they are comparatively 

 economical in the use of water. These 

 characters, while valuable, are all quan- 

 titative. This type of maize does, 

 however, possess one vniique feature. 

 All other types of maize thus far studied 

 produce three or more roots from the 

 seed. These roots support the young 

 plant until the permanent roots that 

 develop from the nodes have been 

 fonned. in the type under discussion 

 there is but one root develo]3ed from the 

 seed. The economy of this arrangement 

 seems to be that the single root is able 

 to penetrate to a greater depth than is 

 possible when the reserve material of the 

 seed is divided among three ormore roots. 



In combination with this character 

 there is also the possibility of a much 

 greater development of the mesocotyl 

 than in other types. The mesocotyl is a 

 specialized organ found in the seedlings 

 of maize and some other grasses. It 

 may be described as the part of the main 

 axis that connects the seed with the 

 first leaf of the seedling. ' So long as the 

 germinating seed remains in the dark, 

 the mesocotyl elongates, stopping only 

 when the tip of the seedling reaches the 

 surface of the ground or the limit of 

 elongation is reached. In planting their 

 maize the Hopi Indians dig into the 

 sandy soil until they reach moist earth, 

 usually found at a depth of from 6 to 1<S 

 inches. The seed is dei)osited in these 

 holes in contact with the moist soil. 

 Although these holes may be left only 

 partly filled, the drifting sand soon fills 

 them, and to reach the surface the voung 



lilants must penetrate from 6 inche.> to a 

 foot of soil. 



Experiments ha\'e shown that com- 

 mercial varieties of mair.e ])lanted under 

 these conditions will not reach the sur- 

 face. The maximum development of 

 the mesocotyl in commercial varieties is 

 from 8 to 10 centimeters. After this 

 elongation is reached the leaves attempt 

 to expand beneath the ground, and as 

 they unfold they are not sufficiently rigid 

 to force their wa\' through the soil. 



It was found that the mesocotyl of 

 Hopi maize is capable of elongating to 

 a length of 36 centimeters or over three 

 times the length attainable in other 

 varieties. At the same time the single 

 strong seminal root is following the re- 

 treating moisture and keeping the young 

 plants alive until the summer rains wet 

 the soil above and allow the develop- 

 ment of lateral roots. A long mesocotyl 

 thus divides the work of reaching mois- 

 ture with the single seminal root and the 

 combination makes possible the estab- 

 lishing of young plants in soils where the 

 nearest available moisture is a foot or 

 more below the surface of the ground. 



These peculiarities make thi.=; type of 

 maize l^cautifully adapted to the condi- 

 tions that obtain on the wind-swept 

 plateaus of northern New INIe.Kico and 

 Arizona where the variety is grown. In 

 this region there is a winter rainfall, but 

 by the time the weather is suthciently 

 warm to warrant the planting of maize, 

 the svtrface soil is thoroughly dry. Sum- 

 mer rains may l)e expected in June or 

 July, but if planting were delayed until 

 the rains came there would not be time 

 enough for the crop to mature before 

 the frosts came in September. 



These adaptations should find an 

 application wherex'er maize is planted 

 during a dry season, and the young 

 l^lants are forced to dei:)end on moisture 

 stored in soil. At San Diego. Cal., the 

 past season plants of this type matured 

 normally without a drop of rain during 

 the growing season. 



That adaptations of so great economic 

 importance should exist inside our own 

 country and remain unnoticed is a 

 striking indication of how inadecjuately 

 the jiossibilities of maize development 

 have been investigated. 



