INFLUENCE OF EXTERNAL CONDITIONS ON GROWTH 



2ÖI 



Neliubov 1 has shown that the form of plants is inlliiciK (<l I. \ 1 Ik 1 

 very small amounts of illuminating gas in the air about them, but especially by 



Fig. no. — Impatiens platypetala; .1. in normal atmosphere; /■>', in atmosphere rich ii 



dioxide. 



1 Neljubow, D., Uebcr die horizontale Nutation der Stengel von Pisum sativum und • 

 Pflanzen. Beih. Bot. Centralbl. ю: 128-138. IQOI. Idem, Geotropismus in der Laboratoi 

 Ber. Deutsch Bot. Ges. 29: 97-1 12. [oil. 



