26 



PLANT PHYSIOLOGY. 



tial to a good experiment house. The pipes must be abundant 

 enough to allow a high temperature, but should be controllable 

 by valves so that it may be lowered to any desired degree. 

 The fifteen separate tables, each 4 feet by 2, and 3 feet 6 inches 

 high (thus high for greater convenience of working standing), 

 are iron-framed, and braced diagonally so as to be immovable 

 when touched (Fig. 3), and have tops of two pieces of smooth 

 slate, which are supported on levelling-screws at the four corners 

 so they may be set level at will, or else are set permanently 



FIG. 3. SECTION THROUGH EXPERIMENT HOUSE. 

 (Compare with Fig. 2.) Scale as in Fig. 2. 



level in cement. The middle one is covered with a shelter of 

 the meteorological sort for thermographs, hygrographs, and 

 other needful instruments. Very essential is the large porce- 

 lain-lined sink with five taps, to three of which are attached 

 respectively a Chapman exhaust, a Boltwood blast, and a small 

 water-motor. A constant-temperature chamber is needed for 

 some purposes, and this can well be obtained by use of such a 

 Wardian case, heated by gas, controlled by a thermo-regu- 

 lator, as I have elsewhere described." It should be set in one 



* ''The Teaching Botanist," page 83. 



