VIII, c, 5 Copeland: Growth of Lagerstroemia 295 
To produce and eliminate during each day curvatures as great 
as these must require decidedly rapid growth in length. The 
tables which accompany the figures show how rapid this growth 
is. On twigs which have not passed through their time of most 
rapid elongation, there are usually some zones whose increment of 
length during twenty-four hours is as much as 100 per cent. 
All of the zones of the younger twigs elongate and the twig as 
a whole is likely to elongate by as much as 60 per cent. Older 
twigs of course grow more slowly than these, and their curva- 
tures are correspondingly less conspicuous. The growing region 
is always a long one, and in most cases a number of zones grow 
about equally fast. However, a few twigs showed zones of 
especially rapid elongation. The greatest increment observed in 
any zone in twenty-four hours was 220 per cent. 
With regard to the hours during which the curvatures took 
place, it was observed that there was not absolute regularity 
but that the different twigs varied by an hour or so in the begin- 
ning of the downward movement and in its progress. In general 
the twigs are straight, or as nearly so as the individual ones 
become, by at least as early as 5 o’clock in the morning. No 
observations were made earlier than this. They retain this 
position for a number of hours longer. By 11 o’clock some, but 
not all, of the twigs begin to curve downward. The curvature 
is slow until about the middle of the afternoon, being most rapid 
between 3 o’clock and 5 o’clock. By 6 o’clock many twigs have 
assumed the night position, while others show some additional 
curvature at 8 o’clock in the evening. 
It is convenient to speak of a day position meaning that which 
the twigs are found in during at least the forenoon, and of a 
night position meaning that observed in the late evening, and 
which is unchanged at least to 10 o’clock, which was the latest 
hour at which observation was made. It should be observed, 
however, that the day position is assumed during the night, and 
that the night position is assumed during the day. 
The position finally assumed by each twig when it ceases to 
grow in length does not differ perceptibly from that which it 
has occupied during the forenoons while it was growing. At 
first sight this seems quite remarkable and it would rather have 
been anticipated that the ultimate position would have been a 
compromise between those previously assumed during the day 
and during the night. The explanation is found in the fact 
that the growing region is longer during the night than during 
the day. Measurements were made of the growth from 6 o’clock 
