EXPERIMENTAL EVOLUTION AMONGST PLANTS. 93 



such pioductious as these of which I have spoken are not to be 

 accepted as species, why should we accept those which we assume 

 would arise under the care of an evolution experiment station? 

 Here we have absolutely new and unique types, as De Varigny 

 demands, and they are as distinct from each other and from their 

 parents, in accepted botanical characters, as "good species" in ' 

 the same genus are from each other, and they perpetuate these 

 characters as unequivocally as those species do. Moreover, we 

 know definitely what their origins were, and they therefore answer 

 all the purposes of experimental evolution. 



Similar observations respecting the evolution of forms of 

 specific importance, could be made for most species of plants 

 which have been widely cultivated for a considerable length of 

 time. The case is singularly well illustrated in Indian corn. 

 Maize lias been very uniformly accepted as a single species by 

 botanists. This arises mostly from the fact that corn is nowhere 

 known truly wild, and has therefore attracted little attention 

 from systematic botanists. There are some authors, however, 

 who have made species of some of the marked cultivated types, 

 either upon the hypothesis that these forms must have been derived 

 from distinct wild types, or that, independently of origin, they merit 

 specific recognition. The chief author who takes the latter view 

 is Sturtevant, who, whilst accepting the common origin of all 

 types of maize, nevertheless prefers to recognize seven "agricul- 

 tural species," as follows: Zea tunicata^ "a primitive form" 

 from which the other six are derived, — Zea everta, pop corns; 

 Z. inclurata, flint corns ; Z. indentata, dent corns ; Z. amylacea^ 

 soft corns ; Z. saccharata, sweet corns ; and Z. amyleasaccharata, 

 , the starchy- sweet corns. Whilst these species are not accepted 

 by the regular botanists, there can be no doubt that some of them 

 would be regarded as distinct species if they should turn up in an 

 evidently wild state ; and a proof of this statement is found in 

 Watson's Zea canina, which was founded upon wild corn collected 

 in southern Mexico. Now Mr. Watson was one of our most 

 conservative American botanists, and any new species which he 

 should describe could be depended upon to have good botanical 

 characters; yet this new Zea canina is so like our rice pop corns 

 that Sturtevant unhesitatingly refers it to his Zea everta, thus 

 showing that it is not more unlike ordinaiy corn than some types 

 of pop corn are ! Moreover, this corn is found to lose quickly 



