xi, c, 5 Copeland: Groivth Phenomena of Dioscorea 229 
However, while the behavior of the different plants from the 
time that a sprout became active until its growth ceased, or 
at least slackened, had so much in common that in a general 
way it can be described as uniform in its larger features, there 
was such irregularity in the time at which this occurred that 
the difference, which would appear at any time between average 
growth in darkness and average growth in light, would have 
been an expression of the number of plants that happened just 
then to be active, rather than of a difference in growth under 
the influence of the illumination. Some plants started, reached 
their maximum rate, and nearly or quite ceased to grow; while 
others remained quite inactive, but retained their power of 
growth, as proved by subsequent behavior. 
Tables II and III shown the growth in millimeters, for one 
day, May 8-9 and for one week, May 9-16, respectively, for 
each of the plants. The exceeding irregularity is seen at the 
first glance. While these tables contain many blanks, indicating 
that the plants in question had not begun to grow, there were 
very few of the entire lot of roots that did not grow before the 
experiment was discontinued, about the end of June. 
There was no rule as to which plants would grow first, except, 
perhaps, that a large tuber was likely to germinate earlier 
than a small one ; even to this rule, there were so many exceptions 
that it would not be worth while to pair the tubers by size and 
to expect them to be comparable in rate of growth at any partic- 
ular time. Some varieties on the average germinated sooner 
in darkness and others in light. On the whole, germination of 
the plants in soil was quicker in darkness than in light. This 
was possibly due to the soil having been kept wetter in the 
dark room; but there was no intention to do this. In the light 
the plants of more than half of the varieties germinated more 
slowly in the bamboo tubes than on the open table. In spite of 
this, my conclusion from observation of the whole series is that 
germination can be hastened somewhat by moisture, but is in- 
dependent of illumination. 
In spite of the diversity of figures in Tables II and III and 
of the further fact that this diversity would be the same if any 
other days or weeks were chosen for presentation, I believe that 
one may conclude from all of the figures that the rate of growth 
of young shoots of Dioscorea is independent of the light. Pfeifer, 
probably on Sachs’s authority, says that this is the case. The 
average growth of all cultures, as has already been noted, was 
