X1TXOGEN A S SIM 1 LA TIO.Y. 



99 



EXPKRLMKNT 32. This 11UIV 1)C tested 



by placing peas in places where no 

 free oxygen is available, and where 

 any gas given off may be tested. Fill 

 a small test-tube with mercury, and 

 invert it over a small dish of mer- 

 cury (as in Fig. 23); support it ver- 

 tically. Soak two peas overnight, 

 remove their coats (to get rid of en- 

 closed air), and slip them under the 

 edge of the test-tube so they may rise 

 through the mercury to its top, mak- 

 ing sure that no air enters between 

 the cotyledons or elsewhere. Test 

 the gas formed after a few days by 

 slipping a piece of potash under the 

 edge of the test-tube. 



D. Metabolism, (c] Xitrogen Assi- 



. FIG. 23. SIMPLE ARRANGEMENT 



milation. FOR STUDY OF I NTRAM()LECU _ 



60. What is the part played by LAR RESPIRATION. (As here 

 ,,.,., ,, T,, j -, . shown, a part of the eras is prob- 



Nitrosren in trie Plant, and wnence is 



3 ably a decay product.) One- 



it obtained 1 half the true size _ 



No experiment upon this subject is practicable ; it is to be 

 worked out theoretically from your various sources of informa- 

 tion. Following are important points: 



(a) Whence comes the nitrogen used b\ r plants ? 



(b ) In what form, where, and by what physical process is 



it absorbed ? 



(c) What is its chief use in the plant ? 



(d } Through what combinations does it pass in the plant, 

 and where ? 



(e) Is free nitrogen ever taken from the atmosphere ? 



(f) How are soils nitrified ? 



D. Metabolism, (//) Use of Minerals. 



61. What is the use or other meaning of minerals in the plant? 

 No experiment on this subject is practicable at present ; it 



