BOTTOM HEAT. 



62 



BOX. 



the air and soil in which any given plant 

 grows naturally. At present, such infor- 

 mation from actual observation is not 

 obtainable ; but it is not so difficult to 

 obtain the maximum and minimum tem- 

 perature of the air of a country, and, 

 these being obtained, the gardener may 

 adopt this as a safe rule : Let the bottom 

 heat for plants of that country be always 

 5 higher than the average temperature of 

 each month that is, if the lowest tem- 

 perature of the month is 44 and the 

 highest 70, the average is 55, and if we 

 add 5 to that, we shall have 60 as the 

 bottom heat for that month. If the average 

 maximum temperature of the air only be 

 known, let the bottom heat be less than 

 10 than the maximum temperature of the 

 air." 



From this we may gather that the bot- 

 tom heat in plant growing, especially as 

 regards exotics, may be and must be suited 

 to the natural climate of the country of 

 which the plant happens to be a native. 

 In raising seeds and striking cuttings of 

 plants which have been brought from other 

 countries, or which, in other words, are 

 not indigenous to our own country, but 

 will germinate or form roots, as the case 

 may be, in the open air in our own land, 

 all that need be done is to raise the tem- 

 perature to summer heat at the utmost, in 

 order to accelerate growth, which would 

 otherwise take place in the natural way at 

 the normal time. If coldness of soil and 

 coldness of the atmosphere forbid growth 

 altogether, or exercise too great a retarding 

 influence on it, it must be remembered that 

 excess of heat in soil and air will draw up 

 plants in telescopic fashion, like children 

 who have grown beyond their strength, 

 and a forced unhealthy growth will take 

 the place of the short, compact, vigorous 

 growth which is the outcome of proper 

 progress. 



As a proof of this, put some seeds of the 



Tropaolum Canariense, and many others 

 of the varieties of the ordinary climbing, 

 Tropseolum, in a small frame in which the 

 bottom heat is high enough to cause the 

 seeds of marrows, cucumbers, and melons 

 to germinate with sufficient rapidity, and 

 note the result. Long and attenuated 

 rowth of the germ of each seed will take 

 place, and presently small leaves of a 

 pale colour will be put forth at the end* 

 of abnormally long leaf stalks, and the 

 stretching out process will be continued 

 from day to day at the same too rapid 

 progress. Tortured into undue growth by 

 improper application of bottom heat, the 

 feeble nurselings are unfit to stand trans- 

 ference into the open air unless measures 

 are taken to slacken the heat gradually, 

 and by a cooling down process to enable 

 the plants to gain strength and tone. 

 Bottom heat is too often applied by 

 amateurs in cases like the above where 

 there is no earthly necessity for it. 



Bourbon Rose- See Rose, Bourbon. 

 Boursault Rose. See Rose, Boursault. 



Boussingaul'tia (naf. oni. Chenopo 



dia'ceae). 



A handsome half-hardy, greenhouse, 

 tuberous-rooted plant, bearing in July 

 copious and graceful racemes of delicious 

 fragrant white flowers. It grows freely in 

 any common garden soil, and will blossom 

 out of doors if planted under a south wall 

 and protected during severe weather. The 

 best known is Boussingaultia baselloides. It 

 is propagated by seeds and division of its 

 tuberous roots. The soil best adapted for 

 its growth is rich loam, with a large admix- 

 ture of peat. 



Box. 



The different sorts of box, Buxus, are 

 very o;aamental. They do not attain 



