176 ' Drying and Wilting of Plants [374 



INCIPIENT DRYING AND TEMPORARY AND PERMANENT 



WILTING OF PLANTS, AS RELATED TO EXTERNAL 



AND INTERNAL CONDITIONS 



By BURTON E. LIVINGSTON 



It has been shown by Renner, 1 by Livingston and Brown, 2 

 by Lloyd 3 and by Edith B. Shreve, 4 that the water content 

 of plant leaves, twigs, etc., is markedly lower after a period 

 of relatively great transpiration (as in the middle of the 

 day) than it is after a period of very small transpiration (as 

 in the latter part of the night). The moisture content of 

 leaves, for instance, was found (Livingston and Brown) to 

 exhibit a diurnal march, the rate of water loss from these 

 organs during the forenoon hours (or even during the 'whole 

 period of sunshine) being greater than their rate of water 

 intake, while the rate of foliar intake of water during the 

 night hours was greater than the rate of water loss. " The phe- 

 nomenon indicated by diminished water content in the day- 

 time was called incipient drying by Livingston and Brown. 

 Renner employed the term sdtigungsdefizit to denote the 

 similar phenomenon encountered in his experiments. The 

 experimentation of all but Renner, of the authors mentioned 



1 Renner, 0., " Experimentelle Beitrage zur Kenntnis der Wasser- 

 bewegung." Flora 103: 171-247. 1911. Idem., " Versuche zur Me- 

 chanik der Wasserversorgung. I. Der Druck in den Leitungsbahnen 

 von Freilandpflanzen. Ber. Deutsch. Bot. Ges. 30: 576-580. 1912. 



2 Livingston, B. E., and Brown, W. H., " Relation of the daily 

 march of transpiration to variations in the water content of foliage 

 leaves." Bot. Gas;. 53: 309-330. 1912. 



3 Lloyd, F. E., " The relation of transpiration and stomatal move- 

 ments to the water content of the leaves of Fonquieria splendens." 

 Plant World 15: 1-14. 1912. Idem., "Leaf water and stomatal 

 movement in Gossypium, and a method of direct visual observation 

 of stomata in situ. Bull. Torrey Bot. Club 40: 1-26. 1913. 



4 Shreve, Edith B., " The daily march of transpiration in a desert 

 perennial." Carnegie Inst. Wash. Pub. 194: Washington, 1914. 



