512 AGRICULTURAL REPORT. 



for the food of man, and without which he could not exist a civilized being, in 

 that they are capable of adaptation, within certain limits, to the varying cli- 

 mates extending from the equator almost to the Arctic circle ; but also, and 

 with renewed cause for admiration, do we perceive how He who made the earth 

 and poised it in space has commanded it should present that aspect to the 

 source of heat and light and life which shall kindly temper his burning rays 

 and divide the seasons, giving to wider zones the moderate springs that shall 

 with increasing mean advance towards the north, bearing with them the 

 warmth, and just the warmth, adequate to mature the wheat, the rye, the oats, 

 and maize, spreading a table for millions of men where, but for this simple 

 obliquity of the axis of the earth, a wa^ste, frozen and inhospitable, would 

 spread its barren desolation to the remorseless skies. 



REMARKS ON THE ACCLIMATION" OF PLANTS. 



It has often been asserted, and is generally believed, that tender exotics may 

 by degrees be accustomed to a colder climate, and thus become acclimatized. 

 Some have believed that by sowing the seeds of such plants, in the first in- 

 stance, in a warm, temperate region, then collecting the seeds produced by 

 these plants and sowing them in colder districts, the species may eventually be 

 rendered hardy. Many plants, it is imagined, have become hardy, which were 

 originally so. We are apt to suppose that plants which grow in tropical coun- 

 tries must necessarily be tender, and adapted only to hot-house culture, not 

 reflecting that they may have grown in very elevated and cold regions in those 

 countries. Such is the case with many species introduced from Japan, Chili, 

 and Nepal, which appear to be hardy in England. Of the dahlia, the heliotrope, 

 the potato, the Lima bean, it may be said long culture has done nothing to 

 increase their hardiness. 



Sound views respecting the geography of plants would correct the prevail- 

 ing errors regarding acclimation. The acclimatizing of plants, or, as it is sup- 

 posed to be, inuring them to lower temperatures than those they have been 

 accustomed to or have required in their native habitate, does not appear to be 

 a possibility. It has been satisfactorily determined that a plant must receive 

 the same amount of heat for the proper performance of certain processes neces 

 sary to the production of leaves, flowers, and fruit, whether in places to which 

 it is indigenous, or far removed therefrom in more northern latitudes. The 

 definite degree which it has demanded during certain epochs of growth is still 

 required wherever it may grow ; but the aggregate of heat may be received 

 during a shorter term in high latitudes because of the greatly increased length 

 of the day, and the processes be hastened and maturity attained at an earlier 

 date. This is well illustrated in the growth of maize or Indian corn, which is 

 said to be remarkably accommodating, though it must have a semi-tropical heat 

 wherever grown, if only for a few weeks, and this heat it obtains even beyond 

 the northern limits of the United States. It is well known that the varieties 

 of maize grown near the northern limit of its -cultivation ripen earlier than 

 those which are esteemed valuable further south. Man has applied to his pur- 

 poses the property possessed by many plants of adapting themselves to the 

 new conditions, and the many varieties of maize, Avheat, &c., attest the possi- 

 bility of change Avithin certain limits. Thus the season required by the maize 

 varies from six months in the elevated plains of Santa Fe, in South America, to 

 four months jn the middle United States, and two and a half months in the 

 Rainy Lake district, northwest of Lake Superior, a seemingly extraordinary 

 transformation of its natural habits and associations. This plant must, how- 

 ever, enjoy for a few weeks, wherever grown, a semi-tropical mean heat of 67°, 

 and the period required for its growth is proportioned to the abruptness of the 

 temperature curve, or the rapid increase and high degree of heat reached during 

 its growth. The several varieties of maize which have acquired the peculiarity 



