228 The Philippine Journal of Science 1916 



I am indebted to my assistant, Mr. R. B. Espino. Of each of 

 thirteen varieties, and working with a single pure strain in each 

 case, ten roots were placed in darkness on a concrete floor, three 

 in darkness in moderately moist soil, ten in the plant-physiology 

 laboratory on a wooden table beside the windows, and three in 

 the latter place, but in bamboo tubes of soil. The names and 

 numbers of the plants used for these observations are given 

 in Table I. 



Table I. — Names and numbers of plants of Dioscorea used in the 



experiments. 



Col- 

 lege 

 No. 



Botanical name. 



Vernacular name. 



88 

 329 

 331 

 938 

 952 

 956 

 958 

 959 

 960 

 1094 

 1101 

 1369 





Tugui. 



Binaksan ube. 



Calut or nami. 



Ube. 



Lagkitang-morado. 



Tumque. 



Sinanto. 



Kinahoy na pula. 



Dinaliri. 



Ube inanislog. 



Apari or tugui baliran. 



Ubeng ligao. 









do 



do 



do 



do 



do 



do 



D. acuLeata. __ 







For darkness, the photographic dark room was used, since 

 it was at that time, April, needed for no other purpose. The 

 dark room and the plant-physiology laboratory are in the same 

 building. Occasional observations showed the temperature to 

 be the same in the two rooms, and there was no evident difference 

 in humidity during the early part of the experiment. During 

 the latter part of the experiment, the soil in the dark room was 

 not kept moist, so that the air there was drier than previously, 

 while in the laboratory, the air became more humid as the rainy 

 season came on. Therefore, growth during the latter part of 

 the period of observation is not available for a judgment as to 

 the effect of light and darkness on the rate of growth. 



With some interruptions, daily growth measurements were 

 made from April 25 to May 26. In presenting statistics of 

 this kind, the use of averages has become usual and one is tempted 

 to present them. With one hundred fifty-six plants in light and 

 an equal number in darkness, it would have seemed that I was 

 working with sufficient material to justify the use of averages. 



