5° 



PLANT PHYSIOLOGY 



Applied Microscopy; there is a useful note by Waugh and McFarland 

 in the Botanical Gazette, 30, 1900, 204; and there is much valualle matter in 

 Smith's " Bacteria in Relation to Plant Diseases" (Carnegie Institution, 1905). 

 A series of white, Llack, and gray screens for backgrounds, arranged to work 

 like roller shades, is very convenient. The most generally useful background 

 for glassware is a sheet of blue blotting-paper. 



Meteorological Recording Instruments. Of these a Thermo- 

 graph for continuously recording temperature, and a Hygrograph for con- 

 tinuously recording humidity, may be considered essential, while a Baro- 

 graph for recording barometric pressure has some, though relatively less, 



utility. These should stand under a 

 proper shelter in the center of the ex- 

 periment house (compare the photo- 

 graph of Plate I). These instruments 

 are very liable to work out of order, 

 and hence should be standardized by 

 comparison with accurate instruments 

 (a good thermometer, a sling or cog 

 psychrometer, and a mercury barom- 

 eter respectively), at frequent inter- 

 vals, — weekly when accurate work is 

 in progress. The various standard 

 forms of these instruments, together 

 with the light recorders or Photom- 

 eters, will be found described in a 

 special section under Transpiration 

 later in this book. 



Mercury Container, an essential 

 feature of any laboratory. After trial 

 of different forms, I have fixed upon, 

 as most efficient and convenient, the 

 arrangement figured herewith (Fig. 9). 

 The mercury, made perfectly clean Ly 

 some one of the methods described 

 under Manipulation in Part III, is 

 contained in a globular separatory 

 funnel, of five inches diameter. From 

 the lower end the mercury is drawn 

 off through a stop-cock ; and into its 

 upper end the mercury is introduced through a funnel, allowing a final filtering 

 through a pin-pricked paper. The funnel is supported by two iron rings 

 of a chemical support -stand, the flat iron base of which rests in, and is firmly 

 screwed to, a large (eighteen -inch diameter) indurated fiber saucer of the 

 stoutest obtainable kind; the tendency of the heavy mercury to bend the 

 support-rod is overcome by a strong wire passing from near the top of the 

 latter diagonally outward and downward to a screw in the base of the saucer. 

 The latter is provided with strong handles (not shown in the figure, as they 



Fig. 9. — Mercury container; Xj. 

 Supported in an indurated fiber saucer. 



