VII. THE INFLUENCE OF GASES AND VAPORS 

 UPON THE GROWTH OF PLANTS. 



EMIL P. SANDSTEN. 



INTRODUCTION. 



In recent years considerable attention has been paid by phys- 

 iologists to the influence of various chemical agents upon the 

 growth of plants, and the results thus far obtained seemed to 

 warrant further investigation along this line. The work here- 

 tofore has been confined almost exclusively to the lower plant 

 forms, which are more easily attacked by the difficult technique 

 which is bound up in this kind of inquiries. The recent prelim- 

 inary results of Johanssen (i) were announced shortly after this 

 work was begun, and it was thought advisable to extend the 

 work to cover the phases of the vegetative period as well as rest- 

 ing seeds, etc. To some extent the writer has had in mind the 

 ultimate application of the reactions obtained in practical garden- 

 ing though such results are reserved for verification and further 

 trial. The work was done during the fall and winter of 1897 

 and 1898 in the laboratories of plant physiology in the Univer- 

 sity of Minnesota under the direction of Dr. D. T. Mac Dougal, 

 to whom the writer is greatly indebted for his valuable advice 

 and kind criticism. 



MATERIAL AND METHODS. 

 The experiments may be conveniently classified as follows : 



1. The influence of gases and vapors upon seeds. 



2. The influence of gases and vapors upon seedlings. 



3. The influence of gases and vapors upon growing shoots. 



4. The influence of gases and vapors upon resting bulbs, 

 corms, etc. 



5. The influence of gases and vapors upon plants growing in 

 water cultures. 



The reagents used were alcohol, ammonia, carbon bisulphide, 



