12 AERATION AND AIR-CONTENT. 



over, that certain marsh plants died quickly when their roots were 

 kept in contact with water charged with CO2. 



Later researches. — As a consequence of the work of Pfeffer and his 

 students, active investigation was directed more to the problems of 

 intramolecular respiration, and direct results relating to normal 

 respiration were largely a by-product. Extensive studies were made, 

 however, of the respiratory curve and quotient during germination 

 and growth at the beginning of this period by Wiesner (1871), 

 Sachsse (1872), Heintz (1873), Deherain and Landrin (1874), De- 

 herain and Moissan (1874), Wolkoff and Meyer (1874), Meyer 

 (1875), Borodin (1875), Detmer (1875), Rischawi (1876), and Saike- 

 wicz (1877). Sachsse and Detmer in particular, together with 

 Muntz (1876), Deherain and Vesque (1876, 1877), and Bonnier and 

 Mangin (1884), gave complete confirmation to the earlier results, 

 which had showed that carbon dioxid was the only gas produced by 

 respiration in all green plants and in most fungi. At the end of 

 this period Pfeffer (1878) declared that it was impossible to ascribe 

 any of the energy used by higher plants to intramolecular respira- 

 tion, and that the share of oxygen in metabolism was so important 

 that normal functioning was impossible in its absence. He regarded 

 the old maxim, ''No life without respiration," as still effective, since 

 normal respiration is indispensable if the organism is to remain 

 capable of life. 



In his study of the respiration of water plants (1875 : 694), 

 Bohm reached the conclusion that the amount of oxygen used in 

 the respiration of water plants in atmospheric air is much smaller 

 than under similar conditions in the case of land plants. Likewise, 

 carbon dioxid is formed by water plants in an atmosphere com- 

 pletely without oxygen or otherwise indifferent, in consequence of 

 intramolecular respiration, but more feebly than under similar con- 

 ditions with land plants. Freyberg and Mayer (1879 : 463) studied 

 the respiration of swamp plants with special reference to the com- 

 parative behavior of swamp plants and land plants. They proceeded 

 upon the assumption that the presence of air-passages was supple- 

 mented by a difference in the intensity of respiration in the roots 

 of swamp plants. Their chief results are expressed in table 1. 



The respiration maximum for the roots of mature swamp plants 

 was 38 c.c. 0, and for seedling roots it was 56 c.c. O, while the corre- 

 sponding maxima for mesophytes were 68 and 83 c.c. The respira- 

 tion was found to increase with the nitrogen-content, and this was 

 thought to explain why swamp and water plants have a uniformly 

 low respiration. The final conclusion was that the roots of swamp 

 plants require less oxygen than those of mesophytes, whether this 

 be determined with respect to volume, mass, or dry weight. 



