VI AUTHORS PREFACE. 



the globe it came. The problem is more diflS-Cult than it 

 appears at first sight. In the last century and up to 

 the middle of the present authors made little account 

 of it, and the most able have contributed to the pro- 

 pagation of erroneous ideas. I believe that three out 

 of four of Linnaeus' indications of the original home of 

 cultivated plants are incomplete or incorrect. His state- 

 ments have since been repeated, and in spite of what 

 modem writers have proved touching several species, 

 they are still repeated in periodicals and popular works. 

 It is time that mistakes, which date in some cases from 

 the Greeks and Romans, should be corrected. The actual 

 condition of science allows ot such correction, provided 

 we rely upon evidence oi varied character, of which 

 some portion is quite recent, and even unpublished ; and 

 this evidence should be sifted as we sift evidence in his- 

 torical research. It is one of the rare cases in which 

 a science founded on observation should make use of 

 testimonial proof. It will be seen that this method 

 leads to satisfactory results, since I have been able tc 

 determine the origin of almost all the species, sometimes 

 with absolute certainty, and sometimes with a high 

 degree of probability. 



I have also endeavoured to establish the number of 

 centuries or thousands of years during which each 

 species has been in cultivation, and how its culture 

 spread in different directions at successive epochs. 



A few plants cultivated for more than two thousand 

 years, and even some others, are not now known in a 



