178 BOTANICAL GAZETTE [February 



respiration are given, the former varying from o. 58 to i .06 and the latter from 

 0.13 to 1.38. 



In every case the young organ, whether leaf, cladode, or branch, had a 

 greater respiratory intensity, a larger respiratory coefhcient, and a lower intra- 

 molecular respiration than the corresponding older organ. This is true 

 whether very young organs or organs in a somewhat later stage of development 

 are compared with fully developed organs of the same year's growth or fully 

 developed organs of the current year's growth are compared with organs of 

 the previous year's growth (leaves of Olea euro pea L.). 



The magnitude of the differences in respiratory intensity between young 

 and old organs varied rather widely in the different species studied, and was 

 evidently related to the relative differences in age. In general the respiratory 

 intensity of the young organs was from 3 to 7 times that of the older organs. 



The author reviews the work of previous investigators, all of whom agree 

 that the respiratory intensity of young organs is greater than that of the corre- 

 sponding older organs. Especially interesting in this connection are the studies 

 of Bonnier and Mangin,^^ of Maige,'^ and of Mme Maige/^ as cited by 

 Nicolas in his article. Bonnier and Mangin found two maxima for respira- 

 tory intensity in the seasonal development of a plant, one at the opening of 

 the leaf buds or at the germinative period, the other at the time of flowering. 

 Maige found that, while the respiratory intensity of flowers decreases with 

 age when calculated on either wet or dry weight, it increases when stated in 

 terms of amount of gaseous exchange per individual flower, and Mme Maige 

 pointed out a decrease in respiratory intensity in each organ of the flower except 

 the gynecium, where it sometimes increases with age. 



The author gives reasons why it is thought that the respiratory differences 

 observed between young and old organs cannot be explained by the absence of 

 well developed cuticle in very young organs, the relative amounts of chlorophyll 

 in the tissues, or the greater acidity of young organs, and raises the question 

 whether they may not be referred to the activities of diastase and oxidase. 

 Finally, the author refers to a previous paper with IMme Maige,^5 in which it 

 was shown that increase in turgescence increases both the respiratory quotient 

 and the respiratory intensity, and concludes that the turgescence of young 



" Bonnier, Gaston, and Mangin, Louis, Recherches sur les variations de la 

 respiration avec le developpement des plantes. Ann. Sci. Nat. Bot. VII. 2:315-364. 

 1885. 



'3 Maige, M. A., Recherches sur la respiration de la fleur. Rev. Gen. Botanique 

 19:1-28. 1907. 



'■t Maige, Mme G., Recherches sur la respiration des differentes pieces florales. 

 Ann. Sci. Nat. Bot. IX. 14:1-62. 191 1. 



'5 Maige, Mme A., and Nicolas, G., Recherches sur I'influence des variations 

 de la turgescence sur la respiration de la cellule. Rev. Gen. Botanique 22:409- 

 422. 1910. 



