GENERAL OBSERVATIONS AND CONCLUSIONS. 457 



These figures show that there are 193 species known 

 to be wild, 27 doubtful, as half-wild, and 27 not found 

 wild. 



I believe that these last will be found some time or 

 other, if not under one of the cultivated forms, at least in 

 an allied form called species or variety according to the 

 author. To attain this result tropical countries will 

 have to be more thoroughly explored, collectors must 

 be more attentive to localities, and more floras must be 

 published of countries now little known, and good mono- 

 graphs of certain genera based upon the characters which 

 vary least in cultivation. 



A few species having their origin in countries fairly 

 well explored, and which it is impossible to confound 

 with others because each is unique in its genus, have not 

 been found wild, or only once, which leads us to suppose 

 that they are extinct in nature, or rapidly becoming so. 

 I allude to maize and the bean (see pp. 387 and 316). I 

 mention also in Article IV. other plants which appear 

 to be becoming extinct in the last few thousand years. 

 These last belong to genera which contain many species, 

 which renders the hypothesis less probable ; ^ but, on the 

 other hand, they are rarely seen at a distance from culti- 

 vated ground, and they hardly ever become naturalized, 

 that is wild, which shows a certain feebleness or a 

 tendency to become the prey of animals and parasites. 



The 67 species cultivated for less than two thousand 

 years (C, F) are all found wild, except the species marked 

 with an asterisk, which have not been found or which 

 are subject to doubts. This is a proportion of eighty- 

 three per cent. 



What is more remarkable is that the great majority! 

 of species cultivated for more than four thousand years ' 

 (A), or in America for three thousand or four thousand , 

 years (D), still exist wild in a form identical with some 

 one of the cultivated varieties. Their number is thirty- / 

 one out of forty-nine, or sixty-three per cent. In cate- 1 

 gories 9 and 10 there are only two of these species of i 



• For reasons which I cannot here express, monotypioal genera are 

 for the most part in process of extinction. 



