252 F. Hück: Pflanzengeograpbie. [30 



3. Quantitative Determination of Factors: (1) Meteorological Records 



(2) Habitat Eeadings (3) Yalue of Instruments (4) Determinable and 



Efficient Differences. 

 4. Instrumentation: (1) Simple Instruments in reconnoissance, and class 



work; (2) Automatic Instruments for resident investigation ; (3) Com- 



bined use of simple and automatic instruments. 



5. Construction and use of Physical Factor Instruments. 



(1) Water content: (1) electrical contact instruments (2) geotome me- 

 thods (3) time and place of readings (4) physical and physiological 

 vvater content (6) checks, rhoptometei-, atmometer, rain-gauge (6) 

 expression of results, water content records, means, sums and 

 curves (7) determination of run-off and ground water. 



(2) Humidity: (1) Psychrometers, sling, rotating and stationary (2) 

 psychrograph (3) methods for reading (4) checks, thermometer, 

 atmometer and anemometer (6) relative and absolute humidities 

 (6) transpiration, potometer, awn hygrometer (7) humidity records, 

 curves, sums and means. 



(3) Light: (1) photometers, air and water (2) auto-photometers (3) 

 Standards (4) comparative readings (5) light values, sums, means 

 and curves (6) determination of reflected, absorbed and trans- 

 mitted light (7) leaf prints, epidermis prints and leaf clinometers. 



(4) Temperature: (1) thermometers, air and soil (2) thermographs (3) 

 contact instruments (4) maximum-minimum thermometers (6) radio- 

 meters (6) checking and standardizing (7) daily and seasonal re- 

 cords and curves (8) internal temperatuves. 



(5) Wind: (1) anemometers (2) anemographs (3) recording vanes (4) 

 checks (6) curves; sums and means. 



(6) Precipitation : (1) rain-guage (2) drosometer (3) snow charts (4) 

 checks, geotome. clinometer, rhoptometer (6) records. 



(7) Pressure: (1) barometers (2) barographs (3) weather and altitude 

 pressures (4) checks (5) records. 



(8) Soil: (1) origin (2) structure (3) water capacity (4) chemical 

 content. 



(9) Physiography: (1) slope, clinometer (2) exposure, compass (3) alti- 

 tude, barometer (4) topography, camera and plane table. 



6. Method of Investigation by Simple Instruments 



(1) Simultaneous readings of temperature, humidity, light and wind. 



(2) Eepeated readings of water content and precipitation. 



(3) Single readings of slope, exposure, altitude. etc. 



(4) Determination of quadrat factors. 



(6) Checking and standardizing simple Instrument by automatic ones. 



7. Expression of Physical Factor Eesults. 



(1) Record sheets for field and permanents records. 



(2) Factor Curves: methods of plotting, level. Station, point and mean 

 curves. 



(3) Factor means and sums. 

 Chapter III. The Plant Formation. 



1. Methods of Reconnoissance, and of Research. 



2. The Quadrat. 



(1) Yalue and uses. 



