CULTIVATIONS AT HIGHER TEMPERATURES. 89 



lamp, without a cylinder, is then placed under the zinc 

 plate, upon which the cardboard boxes are placed, and 

 their temperature is regulated by screwing the lamp 

 up and down until the required temperature is per- 

 manently obtained. If the lamp burns well, and if 

 the apparatus has been prepared carefully enough, a 

 fairly even temperature, scarcely fluctuating for 4°, may 

 be obtained. This is sufficiently accurate for most 

 cultivations. 



