THE FARMERS' REGISTER. 



393 



weiiil< ami sickly, and speedily pieseiiling a dis- , i he cause of the common circumstance of vmea 

 eased appearance. | thai are forced early not seliinir their fruit well, 



On the oiher hand, it is equally well known ihai, j when iheir roois are in the external horder and 

 unless the lemperauire of ih.; soil be raised per- unprotected by arlificiid mchins; and to the same 

 manenlly to a; leasi 75°, the seeds ol tropica! trees cause is often to be ascribed the shrivellinij of 

 will not terminate ; or, if they do, they push lijnh , jfrapes, which, as we all know, most commonly 

 leebiy, and from the first present the sickly ap- i happens to vines wliose rQots arc in a cold and 

 pcarancc of plants sufl'ering li-oni cold. Hence | unsunned border. 



arises the impossiliiliiy of makin<r the seeds of j Mr. Reid of Balcarras has, indeed, shown tiiat 

 tropical plants <jerminate when sown in the open I one of the causes of canker Hnd intmalure fruit 

 air in this coumry, where the mean temperature of l even in orchards is the coldness of the soil. He 

 the earth seldom rises to 65"^, and that /or only /bund that, in a cankered orchard, the roots of the 



s'hort periods ol" time. It is, therefore, obvious 

 that all |)lan.'s require some bottom heat; but the 

 amount varies with their species, and the only 

 means or power of determining what the amount 

 should be, is atl'orded by tlie known degree of 

 warmth of the climate of which a plant may be a 

 native. « 



When plants are cultivated in ixlass houses, 



trees had entered the earth to the depth of 3 leet ; 

 and he also ascertained that, during the summer 

 niunihs, the average heat of tfte soil, at 6 inches 

 below the surliice, was 61°; at 9 inches, 57°; at 

 18 inches, 50^; and at 3 feet, 44^. He took 

 measures to confine the roots to the soil near the 

 surliice, and the consequence whs, the disappear- 

 ance of cariker, and ripening of,the fruit. (J/e- 



there is Utile difficulty in sujiplying them whh \he\m(nrs of Caledonian Ilort. iSbc. vi. part 2- and 

 amount of bottom heat which they may require; j G'arrfe/fcr's il/ngazme, vii. 55.) 

 but this can either not be effected at all, or only j If, on the other liand, we take cases of ffroivlh 

 10 a limited degree by a selection of soils and situ- j in the artificial climate of hot-houses, we find that 



ations, when plants are cultivated in the open 

 air; and hence one of the many difficulties of 

 acclimatizing in a cold country the species of a 

 warmer climate. It is true (hat plants will exist 

 within wide limits of temperature, and, conse- 

 qnenily, a few degreps of difierence in the natural 

 bottom heat to which they are exposed may not 

 afl'ecuhem so far as to destroy thein ; but it can- 

 not be doubted that the conditions most favorHble 

 to their irrovvth are those which embrace a tem- 

 peraiure rather above than below that to which 

 the-v are accustomed in their naiive haunts. 



Theoranize tree is found in perfe<Mion where 

 the temperature of the soil may be cornpu'ed to 

 rise to 80° or 85°, and never to fiili below 58°, as 

 in the Bermudas, Malta, and Canton. How 

 injudicious, then, is our practice of exposiiiir it 

 durinii summer to the open air, in tul>s, where 

 the soil scurcelj' rises in temperature aliove 66^*, 

 and fireserving ii during winter in cold conserva- 

 tories, the soil of which often sinks to 36° ; unde- 

 such circuiustunces the orange exists indeed, bu 



Bitrnonia venusta, and niany other tropical plants, 

 will not flower unless in a i)igh bottom heat; and 

 that palm trees, planted in "the soil of conserva- 

 tories which it is impracticable to lieat sufficiently, 

 soon become unhealthy. 



The reason why it is necessary to plants in a 

 crowing state, that the mean temperature of the 

 earth should be higher than that of the air, is 

 sufficiently obvious. ^Varmth acts as a stimulus 

 10 the vital lorcef^, and its operation is in rn'opor- 

 tion to iis amount, within certain limiis. Ii; then, 

 the branches and leaves of a plant are stimulated 

 by warmth to a greater de-ree than the roots, 

 ihey will consume the sap of the stem faster than 

 the roots can renew ii ; and, therefore, nature 

 tid^escarelo provide against this by giving to the 

 roots a medium permanently more eiir;njlaiing, 

 ihat is, warmer, than to the branches and leave's. 



Such being the liact, it is obvious that one of 

 the first of a gardener's cares should be, to secure 



O..W V,-..... ^c ...^ „.„.,^^ ..^.cto ,.,u..v.u, .,^. ''^ct connected witii this subject:—" It is well known," 



where are the perfume and juiciness of its fruit. 1"^.?^'°' " ^"^^^^ f^*^ ''f'^' of oalc trees is usually stripped 

 and where the healthy visor of its noble fbiiatre ? | ^ '"'1 ?""^' ^u""^ '" ^^^ ^^'"'^ ^'-''^°" "'^ ^""'^"^ 



The vine cannot be grown in the open ^\v oribis\"l,^^ZZ''^''^y^^^^ from their 



,■ P . u . ■ ! amuinum, or sap-wood, from which it is, at that sea- 



country to any useful purpose, except when tr.in- ,on, separated, by the intervention of a mixed cellular 

 ed to walls, in soils and situations unusually ex- and mucilaginous substance; this is apparently em- 

 posed to the beams of the sun; it is only then that i pfoyed in the organization of a new layer of fibre, or 

 it can obtain for its roots such a permanent ' inner bark, the annual formation of which is essential 

 warmth as 75°, which it will have at Bordeaux, i ^o the growth of the tree. If, at this period, a severe 

 or 80° in Madeira. [frosty night, or very cold winds, occur, the bark of 



It may hence be considered an axiom in hor- 1.'^® fr""*^' or main stem, of the oak tree becomes again 

 ticulture, that all plants require tiie soil, as well "''"ily attached to its alburnum, from which it cannot 

 5ihP. airnnsnhprp in r„t,ipt. .I.pv rrrr,.,, ir> n,„>-n J ^'^ ^^P^rated till the letuin of milder weather. Nei- 

 ther the health of the tree, nor its foliage, nor i+s blos- 

 soms, appear to sustain any materiaf injury by this 



as the attnosphere, in which they grow, to corre 

 spend in temperature with that of the countries 

 of which they are natives. It has also been 

 already shown, that the mean temperature of the 

 soil should be a degree or two above that of the 

 atmosphere. 



This explains why it is that hardy trees, over 

 whose roots earth has been heaped or paving laid, 

 are found to suffer so much, or even to die ; in 

 such cases, the earth in which the roots are grow- 

 ing is constantly much coldeir than the atmo- 

 sphere, instead of warmer. We have here,* also, 



sudden suspension of its functions; but the crop of 

 acorns invariably fails. The apple and pear tives 

 appear to be affected to the same extent by similar 

 degrees of cold. Their blossoms, like those of the 

 oak, unfold perfectly well, and present the most healthy 

 and vigorous character ; and their pollen sheds freely. 

 Their fruit, also, appears to set well ; but the whole, 

 or nearly the whole, falls olT just at the period when 

 its growth ought to commence. Some varieties of the 

 apple and pear are much more capable of bearing 

 unfavorable weather than others; and even the oak 

 trees present, in this respect, some dissimilarity of 



* Mr. Knight long since mentioned an important constitution." Hoii. Trans , vi, 229 

 Vol. IX.~33 



