1869.] BOTTOM -HEAT. 569 



at 78° at the bottoms of the pots. When the fruit was fairly visible, the tem- 

 perature of the house was raised 5°, and the temperature of the bed rose gradually 

 to 84°. It has never exceeded this yet, and the earliest plants are now (March 

 12) out of bloom ; the fruit is well above the foliage, robust, and full of promise. 

 The heat of this bed will last for twelve months, and after the fruit is cut off the 

 present lot in June, the succession plants will take their place without any addi- 

 tional fermenting material, and be left till they complete their growth, as we 

 fancy the gradual subsidence of the heat of a leaf-bed more congenial to the 

 perfect maturation of the plants. 



It is better, certainly, to have a command of bottom-heat by means of pipes 

 when needful. Still, though I never made the experiment purposely, I have seen 

 sufficient to convince me that, were the plunging beds of pine-stoves always 

 properly insulated, so that the plunging material would not come in contact 

 with the cold outer walls of the house, whereby it is robbed of its heat. Pines and 

 other things might be grown during summer at least without the aid of pipes or 

 fermenting material, as heat sufficient to maintain healthy root-action would be 

 communicated to the soil from the air of the house. In confirmation of what I 

 say, I will relate an instance that came under my notice here within the last 

 twelve months. One of our pine-stoves, an old house, is constructed something 

 on the principle I have hinted at ; i.e., the pit inside the house is separated from 

 the outside walls by a sunk path which runs all round it. In ^NTovember 1867 

 this pit was filled up with leaves, which were turned over and incorporated with 

 some decayed leaf-mould, the remains of a former hotbed. Cucumbers were 

 grown in the house during winter and spring, and after they were over the bed 

 was levelled down and a lot of succession Pines were plunged in it. By August 

 the Pines were going to rest with a reduced top-heat, and the temperature of the 

 bed stood at 80° ; but when the hot weather of September came it rose to 95°, 

 and as it was continuing to rise we had to move the Pines out to cooler quarters, 

 and no farther notice was taken of it at the time. Before returning the Pines 

 to the same house again in December, I however tested the bed, and found the 

 temperature to be 70°, or about 5° higher than the mean top-heat, which at the 

 time was about 65°, pot vines having been in the house for six weeks. When 

 the bed was originally made up more than a year previous, it was only about 2^ 

 feet deep, so that fermentation could not be very active ; and no doubt the long- 

 sustained high temperature was due to the insulated position of the bed, for in 

 our ordinary lean-to pits the heat of the beds does not last for half the above 

 period. I have no wish to revive obsolete practices, but were I called upon to 

 erect a range of pine-stoves, I would have the beds enclosed within inner walls ; 

 and if a sufficient quantity of leaves was at command to renew the beds par- 

 tially once a-year, I should not fear the result or grudge the little extra labour 

 entailed, if in the end it would be worth speaking of. 



The practice of testing the temperature of hotbeds by means of trial-sticks 

 should be condemned. In experienced hands the plan may be safe, but it is 

 better not to trust to it ; and a thermometer should be placed in every bed, and 

 in a position to indicate the temperature of the soil about the roots of the plants. 

 Unless this is attended to, disappointment will often be the result. 



The Melon will stand a higher temperature at the root than the Pine, and 

 consequently more exposure to the sun. Under the bright sky of Persia, where 

 Melons are said to attain the greatest perfection, the ground must be heated to 

 a high degree ; and as the Melon is a shallow rooter, it must have the full benefit 

 of it. And so we find in forcing that 100° is not too high for its roots in sum- 

 mer, provided the foliage is well exposed to the light and air, and that a high top 



