340 CEREAL PLANTS. Chap. IX. 



cultivated ultimately assumed a yellow colour. But Bonafous 60 

 found that most of those which he sowed for ten consecutive years 

 kept true to their proper tints ; and he adds that in the valleys of 

 the Pyrenees and on the plains of Piedmont a white maize has been 

 cultivated for more than a century, and has undergone no change. 



The tall kinds grown in southern latitudes, and therefore exposed 

 to great heat, require from six to seven months to ripen their seed ; 

 whereas the dwarf kinds, grown in northern and colder climates, 

 require only from three to four months. 61 Peter Kalm, 62 who 

 particularly attended to this plant, says, that in the United States, 

 in proceeding from south to north, the plants steadily diminish in 

 bulk. Seeds brought from lat. 37° in Virginia, and sown in lat. 

 43°-44° in New England, produce plants which will not ripen their 

 seed, or ripen them with the utmost difficulty. So it is with seed 

 carried from New England to lat. 45°-47° in Canada. By taking 

 great care at first, the southern kinds after some years' culture 

 ripen their seed perfectly in their northern homes, so that this is an 

 analogous case with that of the conversion of summer into winter 

 wheat, and conversely. When tall and dwarf maize are planted 

 together, the dwarf kinds are in full flower before the others have 

 produced a single flower ; and in Pennsylvania they ripen their 

 seeds six weeks earlier than the tall maize. Metzger also mentions 

 a European maize which ripens its seed four weeks earlier than 

 another European kind. With these facts, so plainly showing 

 inherited acclimatisation, we may readily believe Kalm, who states 

 that in North America maize and some other plants have gradually 

 been cultivated further and further nothward. All writers agree 

 that to keep the varieties of maize pure they must be planted 

 separately so that they shall not cross. 



The effects of the climate of Europe on the American varieties is 

 highly remarkable. Metzger obtained seed from various parts of 

 America, and cultivated several kinds in Germany. I will give an 

 abstract of the changes observed 63 in one case, namely, with a tall 

 kind (Breit-korniger mais, Zea altissima) brought from the warmer 

 parts of America. During the first year the plants were twelv ; 

 feet high, and a few seeds were perfected ; the low T er seeds in the ear 

 kept true to their proper form, but the upper seeds became slightly 

 changed. In the second generation the plants were from nine to 

 ten feet in height, and ripened their seed better ; the depression on 

 the outer side of the seed had almost disappeared, and the original 

 beautiful white colour had become duskier. Some of the seeds had 

 even become yellow, and in their now rounded form they ap- 

 proached common European maize. In the third generation nearly 

 all resemblance to the original and very distinct American parent- 



G0 Ibid, p. 31. iv. I have consulted an old English 



61 Metzger, 'Getreidearten,' s. 206. MS. translation. 



62 ' Description of Maize,' by P. 63 ' Getreidearten,' s. 208. 

 Kalm, 1752, in 'Swedish Ac^,' vol. 



