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 
969 
960 
1094 
1101 
1369 
D. aculeata var. tiliaefolia 
D. alata 
D. hirsuta 
D. alata 
do 
do 
do 
do 
do 
do 
D. aculeata 
D. alata 
Tugui. 
Binaksan ube. 
Calut or nami. 
Ube. 
Lagkitang-morado. 
Tumque. 
Sinanto. 
Kinahoy na pula. 
Dinaliri. 
Ube inanislog. 
Apari or tugui baliran. 
Ubeng ligao. 
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. 
