The Philippine Journal of Science, C. Botany. 

 Vol. XIII, No. 6, November, 1918. 



ALTERNATE SHRINKAGE AND ELONGATION OF GROWING 

 STEMS OF CESTRUM NOCTURNUM 



By William H. Brown and Sam F. Trelease 



(From the Bureau of Science, Manila, P. I., and the University of the 



Philippines) 



A number of rapidly growing plants in Manila wilt during 

 every comparatively dry sunny day. Conspicuous among these 

 are two vines, Ipomoea nil and Thunbergia grandiflora, and a 

 large shrub with pendent branches, Cestrum nocturnum. That 

 these plants lose more water during the day than they absorb 

 would seem to be self-evident from the fact that they wilt. 

 Livingston and Brown ' have shown that the leaves of mesophy- 

 tic plants growing in Arizona contain considerably less water 

 during the day than at night. Shreve - has shown that this 

 applies not only to leaves but also to stems of Parkinsonia micro- 

 phylla. The size of plant parts is apparently affected by this 

 decrease in water content. Thoday 3 found that the leaves of 

 many plants shrink during the day, so that they decrease in area 

 two or three per cent, or in some cases as much as six per cent. 

 Kraus ' has shown that tree trunks may shrink in diameter 

 during the day, while Darwin 5 has found the same thing to 

 be true of the fruits of Cucurbita, and Smith ■ of the fruits of 

 Artocarpus. 



1 Livingston, B. E., and Brown, W. H., Relation of the daily march 

 of transpiration to variations in the water content of foliage leaves, Hot. 

 Gaz. 53 (1912) 309-330. 



' Shreve, E. B., The daily march of transpiration in a desert perennial, 

 Carnegie Inst. Washington Publ. No. 194 (1914). 



3 Thoday, D., Experimental researches on vegetable assimilation and 

 respiration. V. A critical examination of Sachs' method for using increase 

 of dry weight as a measure of carbon dioxide assimilation in leaves, Proc. 

 Roy. Soc. London B, 82 (1909) 1-55. 



* Kraus, G., Physiologisches aus den Tropen. Ann. Jard. Bot. Buitenzorg 

 11 (1895) 196. 



" Darwin, F., On the growth of the fruit of Cucurbita, Ann. Bot. 7 

 (1893) 459. 



1 Smith, A. M., On the application of the theory of limiting factors to 

 measurements and observations of growth in Ceylon, Ann. Roy. Bot. 

 Gard. Peradeniya 3 (1906) 303. 



353 



