354 • ' BOTANICAL GAZETTE [apml 



present. They also showed that while the roots of Coleus blumei and Helio- 

 tr opium peruvianum show injury in 3 days by an addition of 25 per cent 

 nitrogen to the soil atmosphere, Nerium oleander is unharmed by 50 per cent 

 of nitrogen, and the roots of Salix {nigra ?) grow freely in pure nitrogen. Simi- 

 lar results were obtained by the use of helium instead of nitrogen as a di- 

 luting gas. 



More recently Bergman 11 has found similar differences of response in the 

 roots of land and swamp plants, the dead roots in the former often being 

 replaced by others near the surface of the water, showing lack of aeration to be 

 one of the most important factors involved. Several experiments serve to give 

 emphasis to this fact. He found that land plants with submerged roots soon 

 show pronounced wilting, the wilting being less marked when the submergence 

 is in aerated water, and a reduction in transpiration preceding waiting. This 

 is taken to -indicate that absorption is reduced below the amount demanded 

 by transpiration. When aeration is provided, the use of swamp water for 

 submergence or watering gives no other harmful results than those obtained 

 by the use of tap water or nutrient solutions. The oxygen content of swamp 



nature 



through the Car ex stages to the Chamaedaphne- Andromeda 



mm 



and Larix-Picea stages. This leads to the conclusion that the 

 hydrophytes, mesophtyes, and xerophytes in swamps is due to local differ- 

 ences in habitat, such as water level and aeration, affecting the rate of absorp- 

 tion and its ratio to transpiration; hence ecesis in swamps can occur only 

 when the oxygen requirements of the species are satisfied. 



citations 



ems 



organs 



of individual species to changes in their environment. — Geo. D. Fuller. 



Alpine vegetation of the central Andes. — Hauman 12 has recently described 

 a scanty alpine vegetation found on the Andes between 3 1 and 3 f south latitude, 

 at elevations ranging from 2000 to 42,000 m. This region possesses many peaks 

 above 6000 m. high, the highest and best known being Aconcagua, with an 

 altitude of 7020 m. These mountains are snowcapped and possess a good 

 development of glaciers, from which flow tortuous and variable streams, 

 furnishing almost the entire water supply for the sparse vegetation, since the 

 growing season in these mountains is almost entirely without rain. The 

 temperature records are imperfect, but an important factor is the light frosts, 



Bergman, 



:s influence 



1920. 



12 Hauman, Lucien, La vegetation des hautes cordilleres de Mendoza (Republique 

 Argentine). Anales Soc. Cien. Argentina 86: t^t-tS* bU z-<>? ^c 7. 1018. 



