INFLUENCE OF EXTERNAL CONDITIONS ON GROWTH 263 



phere was not only not favorable to the growth of certain plants but might even 

 be injurious. An increase in the carbon dioxide content, so that this became 



Fig. 109. — Formation of mucor-yeast in an oxygen-free medium. 



A — B 



Fig. no. Impatiens platypelala; A, in normal atmosphere; B, in atmosphere rich in carbon 



dioxide. 



0.2 per cent., resulted in unhealthy plants, which were often very poorly sup- 

 plied with leaves (Fig. no). [But improved growth has been secured in 



