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AMERICAN JOURNAL OF BOTANY 
[Vol. 9 
portance to scientific agriculture, at least for arid regions, since by this 
criterion it may be possible to determine, indirectly, the status of the water 
relations of the plant, and to foresee the need of increased soil moisture, 
long before the usual criterion of cessation of growth or actual wilting 
becomes manifest. The movements of coconut leaves considered in this 
paper suggest a possible use of such changes in leaf position in connection 
with practical agriculture. It seems very important to have easily de- 
termined quantitative methods by which the condition of a crop may be 
judged, as a basis for proper methods of cultivation. The most convenient 
general index of the health of the plant, according to Copeland (3), is the 
growth rate. Although such indices are very much needed, agronomy and 
plant physiology have furnished few that may be conveniently applied, 
mere general inspection usually having to serve as the basis for judging 
the condition of a crop. If changes in the pinna movement of coconut, or 
similar changes in the leaves of abaca and banana (which have been ob- 
served by the writer), represent changes in water content of the leaf tissues, 
measurements of these may prove to be of value in connection with the 
practice of irrigation; the degree of movement or its duration, the hour of 
greatest closing or of maximum expansion, or the range between maximum 
and minimum apparent width, may be of more value as a criterion for 
irrigation practice than mere observations on the appearance of the plant 
or of the soil. The yields of such plants as coconut, abaca, and banana 
might thus be increased considerably by a judicious use of irrigation, even 
in localities having apparently suitable, but not optimal, moisture condi- 
tions. It may even be possible to use plants exhibiting such leaf movements 
as indicators for the irrigation or cultivation of other kinds of crop plants 
whose leaves do not show reversible movements correlated with their 
moisture content. 
BIBLIOGRAPHY 
1. Brown, W. H., and Trelease, S. F. Alternate shrinkage and elongation of growing 
stems of Cestnim nocturmim. Philip. Jour. Sci. C, 13: 353-360. 191 8. 
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Jour. Sci. i: 6-57. 1906. 
3. — — -. Experiments on the coconut I. Philip. Agric. and For. 3: 121-126. 1914. 
4. Darwin, F. On the growth of the fruit of Cucurbita. Annals of Bot. 7: 459. 1893. 
5. Kraus, G. Physiologisches aus den Tropen. Ann. Jard. Bot. Buitenzorg 11: 196. 
1895. 
6. Livingston, B. E. Incipient drying and temporary and permanent wilting of plants, 
• as related to external and internal conditions. Johns Hopkins Univ. Circ. 293: 176- 
182. 1917. 
7. , and Brown, W. H. Relation of the daily march of transpiration to variations in 
the water content of foliage leaves. Bot. Gaz. 53: 309-330. 1912. 
8. , and Hawkins, L. A. The water-relation between plant and soil. Carnegie 
Inst. Wash. Publ. 204: 5-48. Washington, D. C, 19 15. 
9. Lloyd, F. E. The relation of transpiration and stomatal movements to the water 
content of the leaves of Fouguieria splendens. Plant World 15: 1-14. 1912. 
10. — ■ — ■. Leaf water and stomatal movement in Gossypium, and a method of direct visual 
observation of stomata in situ. Bull. Torr. Bot. Club 40: 1-26. 1913. 
