94 Harshberger. — Maize : 



juato, Leon and Puebla, and a glance at a map will show that 

 these localities are situated along the backbone of the conti- 

 nent, below the twenty-second degree of north latitude. A 

 curious coincidence in places must be mentioned. Leon, 

 5400 feet above the level of the sea, is identical with the 

 locality which Professor Duges explored. From the meteor- 

 ological facts we conclnde : 



(1) That maize was a highland plant ; (2) that the original 

 home was south of the twenty-second degree of north latitude ; 

 (3) that the Duges' plant in Philadelphia still preserved the 

 habit of withstanding dry, rainless weather, which the Mexi- 

 can charts show is the summer condition at Leon, its native 

 home. 



B. Botanical Proofs. 



It is a principle of geographical botany that the occurrence 

 of two or more species or genera of close relationship, in any 

 region, indicates the probable origin of those forms within 

 that area. This factor was of little importance to systematists 

 before the days of Darwin and Wallace, but the studies of 

 these two naturalists have served to throw light upon many 

 heretofore obscure problems. 



There is tendency to vary, and variation proceeds along 

 definite lines ; in the mean time, certain forms disappear 

 from the evolutionary series, until it is broken into groups 

 representing new species and new genera of divergent char- 

 acter and form. 



A clear relationship, in many particulars exists between 

 Zea, Tiipsacum and Enchlcena ; and it is probable, therefore, 

 that Indian corn and these two latter plants originated from a 

 common remote ancestor, which grew in Mexico. Maize has 

 diverged most widely from the common type, in having the 

 separate spikes fasciated into a spongy cob. 



The discovery by Professor Duges of the so-called wild form 

 in Mexico adds weight to the argument in favor of a Mexican 

 origin for the plant. The branching habit, the reproduction 

 of the plant by suckers, the small size of the grain, clearly 

 indicate a very primitive condition of the plant. With refer- 



