BOTANICAL GAZETTE. 85 



Now this using of food, called respiration, and common to 

 all life, demands the presence of oxygen, and the question 

 has arisen with regard to plants whether this oxygen is 

 derived directly from the free oxygen of the air or is a sec- 

 ondary product resulting from intramolecular decompositions. It 

 has been observed that germinating plants will continue to evolve 

 carbonic acid in an atmosphere of nitrogen or hydrogen, or in a vac- 

 uum. Wortmann, observing that the amount of carbonic acid 

 evolved from germinating plants was the same when placed in air 

 or in a vacuum, proposed the theory "that all the carbonic acid pro- 

 duced in plant respiration has its origin in intramolecular decompo- 

 sitions ; or, in other words, that the free oxygen of the air takes no 

 direct part in the formation of the carbonic acid in respiration.' 1 

 Dr. W. P. Wilson, an American student at Tubingen, Wurtem- 

 berg, has been experimenting upon this subject, and in the Am. 

 Jour, of Science for June he gives a condensed abstract of some of 

 his results, which will later be published in full. His experiments 

 show that Wortmann's theory falls to the ground because it is 

 founded upon a fallacy. That there is an intramolecular respiration 

 as differing from a normal is easily proved, but that the amount of 

 carbonic acid given off by the former equals that given off by the 

 latter is untrue, for Dr. Wilson's experiments showed, in every case 

 but one, a rapid diminution in the evolution of carbonic acid when 

 he substituted an atmosphere of hydrogen for air. Hence the con- 

 clusion is irresistible that the carbonic acid excreted in plant-respi- 

 ration is a partial product of direct oxidation from the free oxygen 

 of the air. W. Pfeffer shows that even if Wortmann's experiments 

 had been verified his theory would still fail, because "if an equal 

 amount of carbonic acid were formed in both intramolecular and 

 normal respiration this would only prove that the same number of 

 carbon affinities for oxygen had been satisfied in each case, but 

 would in no way indicate from whence the supply of oxygen came. 

 And nrcase free oxygen was active in normal respiration, still in 

 intramolecular, when free oxygen was absent, the full suppty might 

 yet be obtained through constant powerful attractive forces which 

 could take oxygen from other combinations and in this way give 

 rise to secondary changes. 1 ' Dr. Wilson's experiments also verify 

 what has previously been taught with regard to respiration, viz., 

 that the presence of light does not in any appreciable degree direct- 

 ly affect the amount of carbonic acid given off, a capital point to use 

 in contrasting respiration and assimilation. — J. M. C. 



Notes from Northern Iowa. — Psoralen esculent a, Pursh, 

 grows on dry knolls, but rarely matures fruit. This plant, the 

 Pomme cle Prairie of the voyageurs, has large, starchy roots which 

 are quite palatable to a botanist made hungry by a long tramp. 

 P. argophylla, Pursh, is much more common than the former, pre- 

 ferring lower grounds. I have not, after three seasons search, been 

 able to find a single mature seed. It must, however, fruit in favor- 

 able years. 



