264 THE PLAXT WORLD. 



construction of the regulator and in the setting- up of the appa- 

 ratus are shown in the diagram, which is self-explanatory. 



In setting up the regulator, tlie bulb, connecting tube and 

 U-tube are first filled with oil (a heavy paraffine oil has served 

 well), and then clean mercury is poured into the open end of 

 the U-tube. In this operation some oil will escape at the open 

 end of the U-tube. A little oil is left in this arm of the tube 

 to j)revent oxidation. The bulli sliould next be immersed in 

 water of the desired temperature. When tlic oil has taken the 

 temperature of the water, the mercury meniscus of the closed 

 arm of the U-tube is brought just into contact with the sta- 

 tionary pole, this being accomplished by means of a rubber tube 

 temporarily attached to the open end of tlie U-tube. When 

 this is done the stop-cock is closed. Subsequent adjustment is 

 easily made after the apparatus is in place iu tlie oven. 



Tlie Desert Laboratory, Tucson. .Vrizoua. 



EFFECT OF FIRE OX AX AFPLE TEEE. 



About the middle of August last a ])ih' of dry weeds was 

 burned imderneath an apple tree, the heat from the fire shriv- 

 eling the leaves to the top of the tree on the exposed side. A 

 month later the tree came into l)loom wherever the leaves had 

 been fire-killed, but the blossoms failed to set fruit. T have 

 heard tliat strawberrv orowers sometimes fire the beds after the 

 crop has been gathered and that this treatment results in the 

 production of a second crop. — A. O. Garrett. 



The. response obtained l)y l)urning and drying the leaves 

 and twigs of the apple tree above mentioned is probably an 

 example of the similarity of the effects produced upon plants 

 by cold and dryness. The thorough drying out of the buds 

 by the »action of the fire appears to have produced the same 

 effect as the long winter period of low temperatures. In a some- 

 what similar way, an abnormally dry summer and early autumn 

 often produces late autumn flowers upon plants which had their 

 normal period of bloom in the early spring. In the same class 



