116 The Botanical Gazette. (March, 
A factor of much importance in the growth in diameter is 
that of temperature, the plant responding within a short per- 
iod to a rise in temperature by a more rapid growth, and a 
slower growth following a fall in temperature. The term 
growth is used, but it is, of course, understood that the in- 
crease in diameter includes the tension as well, as the results 
of the two are not separable. 
Taking the line of growth for the tomato for Jan. Ist (plate 
XIII), it can be seen that the growth bears a close relation to 
the temperature, the high temperature being followed promptly 
by an increased growth. The total growth for the thirty 
hours can be seen very readily in the line plotted. 
e same points are seen in the lines of growth constructed 
from the record of the potato for Jan. 6th (plate x11). The 
potato gave a much greater growth, but aside from that the 
growth took place in the same manner as in the tomato. On 
these dates occurred the greatest growth obtained from either 
plant. These two have been selected as typical lines of 
growth for the two plants measured. 
In the lines of growth obtained by taking the average 
amounts of growth for the different periods, the effect of tem- 
perature is not so apparent as there were no regular varia- 
tions in the temperature, consequently the average line 0 
temperature is not satisfactory in showing the relation be 
obtained from twelve days’ records. The potato undef ap 
proximately the same conditions gave much the more vigor- 
ous growth, but the records for both of them showed cleatly 
that the increase in diameter was really growth, and not . 
€xpansion that would be followed by a contraction. : 
These observations and comparisons show what is possible 
by the use of the instrument. Further observations are bein 
made in connection with an auxanometer registering growt 
in length, which was also devised by my brother, and is 1" — 
ilar to the one exhibited by Dr. Arthur at the Madison meet- 
ing of the A. A. A. S ee 
Purdue University, La Fayette, Ind. 
