5oo POPULAR SCIENCE MONTHLY. 



ical root-crops is confined to strictly tropical climates, so that increase 

 of latitude and altitude would bring to starch-eating peoples the neces- 

 sity of a change of food plants. Indeed, altitude seems to have played 

 a larger part than latitude in this transformation which brought about 

 the adoption by primitive American peoples of Indian corn, 'Irish' po- 

 tato, arracacha, oca and other crops of the temperate plateaus of South 

 America. Without reasonable doubt, maize is the oldest of cereals, and 

 the large soft kernels which distinguish it from all other food-grasses 

 are exactly the character which would render it easily available to the 

 meal-eating aborigines of America, though it is not to be supposed 

 that the wild progenitor of the Indian corn had any very close sim- 

 ilarity to our cultivated plant. Moreover, everywhere in tropical Amer- 

 ica maize is still prepared by methods adapted to root-crops instead of 

 as a cereal. The rough stone slab (metate) against which they had 

 rubbed their cassava or other starch-producing roots was well suited to 

 making paste from maize, softened by soaking in water with lime or 

 ashes, and throughout tropical America it has remained in use to the 

 present day. Among the tribes of the arid temperate regions where 

 the tropical root-crops were excluded the metate was deepened into the 

 mortar in which seeds too small to be collected or handled singly are 

 also bruised into meal. 



It is also not impossible that maize was the first plant to be grown 

 by man from seed, a cultural method permitting much easier and more 

 rapid distribution than had been practicable with the root-crops grown 

 from cuttings and tubers. Like other species cultivated in the high- 

 lands of tropical America most varieties of maize do not thrive in moist 

 equatorial regions of low elevations, so that it did not seriously supplant 

 the root-crops, though having a far wider distribution than any other 

 plant cultivated by the aborigines in pre- Spanish America. Nor did 

 the utilization of maize mark the limit of cereal cultures in America, 

 though no other small foodseed of the new world compares in popu- 

 larity with rice, wheat, barley, rye and oats. Even in Mexico, the sup- 

 posed home of maize, the seeds of Amaranthus and Salvia (Chia) 

 attained considerable economic importance. In addition to their use 

 as food the latter were made to furnish a demulcent drink and an edible 

 oil valued as an unguent and in applying pigments, a series of functions 

 closely parallel to those of sesame, perhaps the most ancient of old 

 world herbaceous seed-crops. Wild seeds of many kinds were collected 

 by the Indians of the United States and Mexico, including wild rice 

 (Zizania) and Uniola, another rice-like, aquatic grass of the shallow 

 shore-water of the Gulf of California. In Chili there existed also sev- 

 eral incipient cultures of small-seeded plants, such as Madia, while the 

 people of the bleak plateaus of Peru and Bolivia had developed a unique 



