1893- NOTES AND COMMENTS. 413 



by what we know of fossil Conifers ; Walchia, a genus allied to the 

 subgenus Eutacta of Arancaria, appears in the Upper Carboniferous, 

 while the pines begin only at the Lias. On the other hand, it is 

 generally agreed that the Abietineae show close affinities with the 

 Araucarieae. 



The Respiration of Plants. 



In Pringsheim's Jahrbiicher] (vol. xxv., p. i) there Is an 

 account of some investigations by Anton Amm on the intramolecular 

 respiration of plants. With regard to the relations between the 

 amount of carbonic acid produced in this function and the degree of 

 temperature to which the plants were exposed, it was found that the 

 minimum temperature, as in the case of normal respiration, was 

 below freezing point, since at o^ C. a significant amount of the gas 

 was given off. As the temperature rose, intramolecular respiration 

 also gradually increased, but this increase was not proportional to the 

 rise of temperature. In both Wheat and Lupine seedlings the 

 optimum was reached at 40"^ C, which coincides with the optimum 

 for the normal process. On the other hand, while there is, doubtless, 

 a maximum temperature for the latter function, in the case of the 

 wheat plant and Lupiniis lutens somewhere about 45^ C, there can, 

 properly speaking, be no such point in the intramolecular process, 

 since in absence of oxygen, seedlings cannot stand temperatures 

 between 40'^ and 45° C. without prejudice to their vitality, and the rapid 

 fall in the respiration curve when the optimum temperature is passed 

 is due to the commencement of death. 



The author finds the relation between the amounts of carbonic 

 acid formed in the normal and intramolecular processes to vary with 

 the temperature. Thus in the case of the wheat the relation ^ 

 decreases in passing from 0° to 25° C, and then increases regularly up 

 to 40^ C. The values obtained with the Lupine, except for some 

 fluctuations, show a similar fall and rise ; the minimum is, however, 

 reached at 35° C, not 25° C. 



The relation between the amounts of carbonic acid gas formed 

 in the two processes varies in different stages of development of one 

 and the same plant, the fraction ,^- increasing with increasing 

 development. The present investigations have also supplied fresh 

 confirmation of the fact that, by the withdrawal of oxygen, production 

 of carbonic acid at once sinks in amount but remains constant for a 

 long time at the lower level, and immediately rises again to the 

 original amount when oxygen is again supplied. 



Finally, the results show that the difterent organs of a plant, e.g., 

 flowers and leaves, give an almost identical relation between the 

 normal and intramolecular respiration, while the organs of different 

 species show quite a different relation. 



The paper includes an account of the apparatus and methods 

 used in these researches, as well as an historical review of the subject. 



