DAILY RHYTHMS IN CERTAIN ROOTS 
Curtiss (5) has noted, under constant illumination, rhythms in the rate of 
transpiration of certain plants. A pronounced maximum occurs near 
midday, with other minor oscillations. He has further noted that the 
stomata are more responsive to stimuli in the morning than in the afternoon. 
From the foregoing account of earlier work it is seen that in all cases 
when plants are exposed to the normal alternation of darkness and light a 
regular daily ''periodicity" is thus induced; and that when these conditions 
are rendered uniform this ''periodicity" is gradually lost. From the work 
of Kellicott (14), Karsten (12), and from the results of the present paper, 
it is seen that there is present, under uniform conditions, a "rhythm" 
which is entirely independent of the "periodicity" induced by environ- 
mental changes. This rhythm is concealed by the more prominent perio- 
dicity under normal conditions. Previous workers, including both Kellicott 
and Karsten, have failed to point out this difference. It is the object of 
this work to determine to what extent these rhythms are present in other 
species than those mentioned above, their probable cause, and their relation 
to the time of day. 
Materials and Methods 
Materials 
For the present study the following materials were used: radicles from 
seedlings of Cucurhita Pepo L., Lupinus albus L., Pisum sativum L., Vicia 
faba L., Allium Cepa L., and Zea everta Sturt.; and roots from germinating 
bulbs of Allium Cepa h., A. canadense L., and A. cernuum Roth. 
Methods 
Elongation. Seeds or bulbs were germinated in moist sawdust loosel^^ 
packed in glass germinating chambers. These chambers had one face ground 
plane and polished, and measured 75 x 100 x 400 mm. The plane face was 
ruled in horizontal lines 2 mm. apart. Germination, except in a few cases, 
was secured at temperatures constant to within one degree C, though the 
temperatures used in different series ranged from 22° to 26° C. The 
cultural chambers were kept tilted a few degrees from the vertical while in 
the incubators, in order to have the root tips always growing directly along 
the inside of the chamber face. When observations were to be made, the 
chambers were taken from the incubators and placed before a horizontal 
microscope fitted with an eye-piece micrometer. The exact position of the 
tip of the growing root was then determined by measuring the number of 
micrometer spaces between it and the horizontal lines (on the face of the 
chamber) below and above it. In this way the exact position of the tip of 
the root was determined every hour throughout the course of the experiment, 
and the increments of growth calculated from the changes in this position. 
Since one eye-piece (micrometer) division was equal to 0.04 mm. absolute 
measurement, the growth increments could be measured accurately to 
o.oi mm. 
