Collins: Pueblo Indl\n Maize Breeding 



263 



through eight cm. of soil. In all of the 

 Navajo plants the coleoptyle reached 

 the surface. 



The extent to which the Chinese and 

 Boone seedlings were able to penetrate 

 the soil by means of the true leaves was 

 doubtless much greater in the carefully 

 prepared soil of the experiment than 

 would be the case under field conditions 

 where any slightly compacted lump of 

 soil would deflect the tender leaves and 

 cause them to crumple. On the other 

 hand, many seedlings failed to come up 

 where there was less than two cm. 

 between the top of the coleoptyle and 

 the surface of the groimd. The results 

 clearly show that the coleoptyle is the 

 proper organ for penetrating the soil 

 and where this office devolves upon the 

 leaves, germination is uncertain. 



It has been observed in many field 

 plantings that the spatulate first leaf, 

 formerly called the cotyledon, is the 

 first evidence of the germinating plant. 

 When this occurs in any considerable 

 proportion of the plants, it is safe to 

 assume that the seed has been planted 

 too deep for the best results. 



In examining these experimental 

 plants it was observed that the root 

 system of the Navajo variety differed 

 from that of the other varieties. The 

 roots of the Navajo seedlings extended 

 to a greater depth, but there was only 

 a single root arising from each seed, 

 while in the Chinese and Boone seed- 

 lings the roots were shorter and more 

 nimierous. Further experiments with 

 Hopi and Zuni varieties showed them 

 to be like the Navajo variety in pro- 

 ducing but a single root from the seed. 



The roots of maize are of two kinds, 

 those that rise from the embryo or seed, 

 called seminal roots, and those produced 

 from the nodes of the plant. Of the 

 latter class, those that arise from the 

 nodes above the grormd are often called 

 brace roots or aerial roots. In the 

 varieties commonly grown in the United 

 States there are, in addition to the 

 primary root or radicle, from two to 

 six additional roots that arise from the 

 base of the cotyledon. These secondary 

 seminal roots, though appearing some- 

 what later, usually equal or exceed the 

 radicle in size. In the Pueblo varieties 

 of maize these secondary seminal roots 



have been absent in all seedlings thus 

 far examined, the radicle being the only 

 root arising from the seed (see Figures 

 8 and 9). 



field studies of pueblo maize. 



In September, 1913, opportunity was 

 afforded for a short visit to the Zuni, 

 Navajo and Hopi Indian reservations 

 of Arizona and New Mexico. It was 

 thus possible to form some idea of the 

 agricultural significance of the peculi- 

 arities and habits of germination of this 

 type of maize. 



The value of deep planting made 

 possible by the greatly elongated meso- 

 cotyl was obvious. In the localities 

 selected by the Indians for planting 

 maize the soil is sandy and in the 

 absence of spring rains the surface 

 layers are, of course, very dry. The 

 seed, to germinate at all, must be 

 planted deep enough to be in contact 

 with the moist soil. In Navajo fields 

 near Tohachi, N. M., plants were dug 

 up and the remains of seeds were found 

 at depths ranging from five to seven 

 inches below the surface. Similar 

 depths were found in a Zuni field near 

 Black Rock, Arizona (see Figure 10.) 

 In a Hopi field at Polacca, Arizona, 

 near the first mesa, where the conditions 

 are extreme, the seed had been planted 

 at 10 inches from the surface. It thus 

 appears that there is no fixed depth for 

 planting, the custom being to plant 

 deep enough to place the seed in moist 

 soil. If the seed were planted at or- 

 dinary depths, germination might be 

 delayed until the latter part of June or 

 the first of July, at which time the rains 

 usually occur, or if the seeds germinated 

 as a result of one of the occasional 

 showers occurring in May, the plants 

 would die from subsequent dessication. 



Like the long mesocotyl, the simple 

 radicle of the Pueblo maize may be 

 looked upon as an adaptation to the 

 extreme conditions that exist where 

 this type is grown. For six or eight 

 weeks after planting no rain can reason- 

 ably be expected and during this time 

 the moisture is constantly receding 

 from the surface. By concentrating the 

 energy of the seedling into a single root 

 the latter is forced to greater depths and 

 consequently kept in soil that is more 



