CHAPTER ni 



INFLUENCE OF EXTERNAL CONDITIONS ON GROWTH 

 AND CONFIGURATION! 



§1. Dependence of Growth and Configuration upon Temperature.— 



Medium temperatures^ are most favorable for growth, which ceases with very 

 high and with very low temperatures. The following table shows the incre- 

 menrs of elongation of three plants for a forty-eight hour period, at various 

 temperatures. 



The minimum, optimum and maximum temperatures for the growth of 

 several different plants are shown in the next table. This table shows clearly 



Eordeum vulgare (barley) 



Sinapis alba (white mustard) 



Lepidium sativum (garden cress) 



Phaseolus multiflorus (scarlet-runner bean) 



Zea mais (maize) 



Cucurbita pepo (gourd, squash) 



Minimum 



deg. C. 

 S-o 

 o 



I 



9 



9 



13 



Optimum 



deg. C. 

 28.7 

 21.0 

 21.0 

 33.7 

 33-7 

 33-7 



Maximum 



deg. C. 



37-7 

 28.0 

 28.0 

 46. :j 

 46.2 

 46.2 



' [On plant movements in general, see: Pringsheim, Ernst G., Die Reizbewegungen der Pflanzen. 326 p. 

 Berlin, 1912.I 



' KSppen, W., Warme und Pflanzenwachsthum. Bull. Soc. Imp. Nat. M0SCOU43 : 41-110. 1870. 

 Sachs, J., Physiologische Untersuchungen fiber die Abhangigkeit der Keimung von der Temperatur. 

 Jahrb. wiss. Bot. 2 : 338-377. i860. 



223 



