24 



now CHOPS PEED. 



was placed in a basin ot'uiereury, C, D, to shut off its con- 

 tents from the external air. So much water was intro- 

 duced as to reach the ends of the j^-iucipal roots, and the 

 space above was occupied by com- 

 mon or some other kind of air. lu 

 one experiment carbonic acid, in a 

 second nitrogen, in a third hydro- 

 gen, and in three others common 

 air, was employed. In the first the 

 roots died in seven or eight days, 

 in the SL'Cond an^l thii-d they perish- 

 ed in thirteen or fourteen days, 

 wliile in the three others they re- 

 mained healthy to the end of three 

 weeks, Avhen the experiments were 

 concludeil. {Recherehes, p. 104.) 

 Flowers require oxygen for their 

 development. Aquatic plants send 

 their flower-buds above the water 

 to blossom. De Saussure found 

 that flowers consume, in 24 hours, 

 several or many times their bulk of oxygen gas. This 

 absorption proceeds most energetically in the pistils and 

 stamens. Flowers of very rapid growth expeiience in 

 this process, a considerable rise of temperature. Garreau, 

 observing the spadix of Arum itaUcum, which absorbed 

 28|^ times its bulk of oxygen in one hour, found it 15° F. 

 wai'mer than the surroiuiding air. In the ripening of 

 fruits, oxygen is also absorbed in small quantity. 



The Function of Free Oxyg^en. — AH those processes 

 of growth to which free oxygen gas is a requisite appear 

 to depend upon the transfer to the growing organ of mat- 

 ters previously organized in some other part of the plant, 

 and probably are not cases in which external inorgani(? 

 bodies are built iip into ingredients of the vegetable struc- 

 ture. Young seedlings, buds, flowers, and ripening fruits^ 



Fig. 2. 



