GREENHOUSE AND LABORATORY 



4i 



elementary courses by use of a Wardian case, which should be 

 placed before a large (preferably a bow) window. Plants will 

 thrive in such a case, some kinds even better than in larger spaces. 

 The case should be as nearly air-tight as possible in order to 

 shield the plants from the worst of the gases of the room, and 

 should preferably be ventilated at intervals by fresh air from 

 the window. If the room is kept constantly warm all around 



<•' 





Fig. 5. — Ventilated dark box for physiological use, in longitudinal 



section; XsV- 



The doors and table are dotted, and the lower figure shows the construction of the doors, 

 which are held in place by buttons. The case is half as deep as it is broad. 



the case, no artificial heating will be required, but if the tempera- 

 ture falls very low at night, the case should be heated either by 

 a gas-jet beneath a galvanized-iron box forming the bottom of 

 the case, or, much better, by an incandescent electric heating 

 coil controlled by one of the thermo-regulators earlier mentioned 

 (page 37, note). I have given somewhat fuller details con- 

 cerning Wardian cases and their construction in my "Teaching 

 Botanist," page 82. In such a case, as I know by trial, many 

 of the simpler physiological experiments with living plants can 



