618 



FARMERS' REGISTER 



L.Nu. 10 



The effect of ditierences in climate is not so 

 great in thie case of some plants as in thalof'olliers. 

 Tiie results of many observaiions rcspeding ihis 

 matter are, Isf, endo(iens, such as the palms, 

 which are destitute of a (listirn't liarU, are much 

 more sensibly atlectetl hy sudden changes of tern- 

 |)erature than exogens, such as the oak ; 2iul, 

 plants of a dry nature, resist cold nnich belter 

 than such as are waters', and indeed all plants re- 

 sist cold belter in dry winters, than in moist ones ; 

 3rd, as a {general thinjr, trees which lose their 

 leaves during the winter resist cold better than 

 such as retain them, and of those which retain 

 their leaves, resinous trees, belter than those which 

 are not so; 4th, herbs, the roots of which are pe- 

 rennial, all resist better than those whose stalks 

 and leaves are persistent; 5ih, annuals which 

 flower late, and whose seed lie dormant in the soil 

 till the succeeding spring, stand the winter better 

 than those which flower early, and whose seed 

 drop and germinate before winter. 



The causes which have most influence in deter- 

 mining the climate of a country are, distance from 

 the equator, elevation above the level ot the sea, 

 and the nature of the suriace. Without entering 

 into a philosophical examination of the manner in 

 which climate is affected by each of these causes, 

 it may be worth our while to attend to a taw facts 

 respecting the extent to which each of tliem does 

 affect climate, in order to ascertain their efiect on 

 vegetation. 



From a comparison of a great number of obser- 

 vations made by Humbolt and others, in different 

 parts of the world, it appears that a dilfeience in 

 latitude of one degree, causes a difference in the 

 mean temperature of lo Fahr. ; and that a differ- 

 ence in elevation above the level of the sea of 400 

 feet, produces about the same effect. "jVlouniains 

 1000 fathoms or 6394 English feet in height, in 

 46° north or south latitude, have the mean tem- 

 perature of Lapland ; mountains of the same 

 height between the tropics enjoy the temperature 

 of Sicily; and the loiiy summits of the Andes, 

 even where situated directly under the equator, 

 are covered with enow as eternal as that ol" the 

 north pole." ''At the foot of iMount Ararat," says 

 Tournaport, "I met with plants peculiar to Arme- 

 nia ; above these with plants which are common 

 in France ; at a still greater height I found myself 

 surrounded with such as irrow in Sweden ; and at 

 the summit with such as vegetate only m polar 

 regions." 



The nature of the surface of a country also af- 

 lects its climate. The presence of high moun- 

 tains always renders a country colder tb.an it would 

 otherwise be; proximity to the sea renders a coun- 

 try cooler in the summer and warmer in the win- 

 ter; a country whose surface dips towards the 

 eonth is much warmer than one in the same lati- 

 tude vvhose surface dips i<nvards the north. It is 

 a llict which has long been known that countries 

 in America and Asia, are much colder ihan <hose 

 of Europe in the same latitude. American plants 

 veifeiaiing at 42" north latitude, will veyetiite at 

 52^in Europe. The low temperature of America 

 as compared with that ol Europe, is owinu prin- 

 cipally to the existence o( iirtmense tracts of wood 

 land and vast marshes in the former, which are 

 emirely wanting in the latter. The low tempera- 

 ture of many parts of Asia is owing to their great 

 elevation above the level of the sea; almost the 



whole of central Asia is described by travellers as 

 a vast plane, olevnted many hundred I'eet above 

 the level of the sea. Africa is much hotter wiihin 

 the tro()ics, than the corres])ondin<; f)arts of South 

 America, because in the latter ihe temperature in 

 lowered by the presence of immense chains of 

 mountains, whilst in the fljimer it is increased by 

 the hot and burtiiiiir sands which cover so large a 

 portion of its suriace. 



The influence of elevation upon the climate of 

 a country, accounts lor the great variety of plants 

 which are Ibund indigenous to mountain districts. 

 It has been laid down as a botanical axiom, that 

 the more diversified the surface of any country ig, 

 the greater will be the variety of plants Ibund glow- 

 ing in it. 



From the remarks which have been made re- 

 specting the influence of climate upon vegetation, 

 it must not be inli'rred, that the same plants will 

 always be fbumi growinij in countries which re- 

 semble each other in that respect; for whilst two 

 countries may be equally well adapted to the 

 growth of particular plants, there may be causes 

 which will effectually prevent those which are na- 

 tives of one country from becomingspread through- 

 out the other. Oi" such a character are, the exis- 

 tence of sandy deserts, so extensive that seed can- 

 not be carried across them by any natural means; 

 seas so vast that seed cannot be drilled in saleiy 

 from one shore to the other; and long and lolty 

 chains of mounlains. To these causes it is that 

 we must trace the fact that countries resembling 

 eaeh other in climate and soil, do not always pro- 

 duce the game plants. '"Thus in certain parts of 

 North America, which closely resemble tliose of 

 Europe, not a single Eurojiean plant is to be found. 

 The same remark will iipply to New Holland, the 

 Cape of Good Hope, Senegal, and other countries, 

 as compared with other countries similarly situated 

 as to their physical circumstances." The separa- 

 tion of Africa and South America, if they ever 

 were united. Hunt bolt remarks, must have taken 

 place "betbre the developemenl of organized be- 

 ings, since scarcely a sinirle plant of the one coun- 

 try is to be found in a wild state in the other." 



The character of the soil as well as the nature 

 of the climate, has a great influence in determin- 

 ing the habitation of plants. This may arise Irom 

 several causes. Among the more important of 

 I these are : 1st. The lijct that some plants re- 

 I quire certain peculiar substances not conmion to 

 I all soils, in order to perfect their organic struc- 

 I tores. Thus silex enters largely into the conipo- 

 ! sition of the bark of the cane, and unless this sub- 

 I stance be present in the soil, it will of course be 

 impossible lor that plant to perfect its stem ; car- 

 ; bonate of soda is a necessary element in the sal- 

 sola, and in no soil but one furnishinir carbonate 

 of soda can the salsola grow. 2nd. The peculiar 

 texture of a soil depends very much, perhaps we 

 might say, entirely, upon the nature of the sub- 

 stances of which it is composed. A silicious soil 

 is alvva3's loose and porous, an argillaceous soil is 

 always close and stiff". A loose porous soil it is evi- 

 dent is much better adapted to the healthy growth 

 and rapid propagation of such plants as have large 

 and fleshy roots, or as develope tubers or under- 

 ground stems, than a close, and stiff one ; so that 

 if we should suppose that in the first place, one ot' 

 this species of plants was equally diffused in all 

 kinds of soil, the whole tendency in the one case 



