MARCH. 



37 



The application of bottom heat to out-door cultivation, or geothermal culture 

 as it is now termed, is beginning to claim attention as a powerful auxiliary for 

 growing a variety of useful and ornamental plants in the open air, which would 

 fail without its assistance. For the present I will confine myself to the house 

 culture of fruits, where I believe its more general employment would confer 

 advantages scarcely yet appreciated. In walking round the houses at a cele- 

 brated nursery the other day, I remarked the great vigour of a Vine growing 

 in a 10-inch, pot, and which formed a rod equal to what is not frequently 

 grown in a rich border ; the pot rested on the hot-water pipe just where it 

 entered the house from the boiler, and, consequently, the roots of the Vine in 

 question were exposed to its influence. The strength of this plant, which 

 exceeded all the others, had not escaped the notice of the worthy proprietor, 

 and he attributed its superiority to the extra bottom heat the plant had enjoyed. 

 I have frequently noticed how much longer Cucumbers will continue produc- 

 tive when subjected to a steady bottom heat ; whereas, when this has been 

 allowed to decline, the plant seems to stop further growth and give up further 

 bearing. In the spring of this present year, two lots of the same batch of 

 Strawberries were selected, one-half of which were plunged in a slight bottom 

 heat in a glass pit, the other half placed in the ordinary way on the shelves of 

 a forcing-house, the plants at the time were just showing the bloom.-trv.sses. 

 I gave those plunged nothing but clear water ; while the other had good 

 liquid manure each second watering ; yet, although these latter had greater 

 advantages of light and air over the other, they ripened only three days earlier, 

 while those in bottom heat produced fully one-third more in bulk of fruit, 

 which was altogether finer, several of the fruits weighing 1% oz. each ; the 

 variety being the Oscar. One thing as regards this experiment struck me as 

 fully confirming the view I have long held on .this subject, which is the length 

 of time which the plunged plants would have continued in bearing, had I 

 wished them to do so, for strong trusses of bloom were showing themselves 

 before the last fruit was gathered ; and I consider that this varietv, and one 

 or two others, if plunged in bottom heat for the first crop, and allowed to 

 remain, a second might be obtained within a short time — a fact which may 

 have weight when plants are scarce. The rationale of the system appears to 

 be this : the more active the roots of any plant are kept the more food will 

 they take up, and the greater the number of leaves will they supply with the 

 elements for assimilation. Subjected to a uniform bottom heat, the roots are 

 maintained in a constantly excited state, and it is possible to imagine the 

 roots of a Vine confined to a 10-inch pot one mass of active spongioles 

 requiring to be fed, perhaps several times daily, with food. We can also 

 imagine that with this mass of roots so completely under control as to heat, 

 the plant only requires to be properly supplied with food to nourish and per- 

 fect as large a crop as the amount of foliage on the plant would enable it to 

 ripen perfectly ; and, if I am correct in this, it is easy to calculate what 

 immense crops may be obtained through pot culture — through the application 

 of bottom heat. I do not wish to limit these observations to the Vine alone, 

 for I am clearly of opinion that the Peach, Nectarine, Apricot, and Fig, would 

 be influenced in an equally favourable manner by the same method of treat- 

 ment. Under all circumstances I give the preference to setting the pots over 

 a heated chamber or a series of pipes, to plunging them, owing to the difficulty 

 of confining the roots inside the pots when plunged ; otherwise, where the heat 

 can be kept up without much inconvenience, or subjecting the plants to any 

 great change, it will answer equally. 



The advantages of bottom heat to such forced fruits as we have named, 

 appear to be in promoting an earlier growth and maturity of the wood, and, 



