474 
The Ohio Naturalist. 
[Vol. XII, No. 4, 
THE DIURNAL1NODDING OF THE WILD CARROT AND 
OTHER PLANTS. 
John H. Schaffner. 
Many plants exhibit periodical movements during the twenty- 
four hours of a day. Among the more interesting of such move- 
ments is the daily nodding in the evening, shown by a number of 
species common along the roadside. 
During the past summer the writer obtained considerable 
pleasure in making observations on some of the common plants of 
Columbus. One of the most striking in this respect is the wild 
carrot (Daucus carota L.) In thrifty plants there are usually a 
number of branches which all begin to nod at an early age and 
continue the habit until the plant is in full bloom. The best time 
to study this peculiar phenomenon is from the middle of June to 
the middle of July. The long peduncles, bearing the young 
umbels nod before the sun goes down, the curving being prominent 
by six o’clock. The various branches nod in a radial manner 
outward from the central axis of the plant. The length of time 
taken to develop the curve was not ascertained but it was 
observed that the peduncles are erect in the morning and remain 
so during the day. Late in the afternoon, the curving begins and 
continues until in some cases the peduncle describes nearly a 
circle. The nodding is most striking just before the blooming 
period in plants with numerous long peduncles. At this period 
the umbel frequently moves through an angle of over 270°. 
Frequently the upper face of the umbel touches the side of the 
peduncle. The diameter of the curve in a medium sized peduncle 
is about two inches. The curved peduncle is quite rigid and should 
show an interesting cellular condition if properly studied. The 
diurnal nodding of the peduncle stops at the time of anthesis, 
although there are subsequent interesting movements in the rays 
of the umbel itself at a later period. 
The common Dogfennel (Anthemis cotula L.) also has the 
diurnal nodding habit. Its numerous lateral branches bearing 
heads of flowers nod in the evening and at night and become erect 
again early in the morning. The nodding takes place in the 
same radial manner as in the wild carrot. 
In Lactuca hirsuta Muhl., before and during anthesis a decided 
drooping or nodding of the large flower cluster occurs, the main 
axis bending about six inches from the tip. The stems were 
found erect in the morning. Euphorbia nutans Lag., as its 
name indicates, also has a nodding of the tips of the stems each 
evening and a return to the erect position in the morning. 
One may well ask as to the purpose of the nodding habit so 
prominently developed in the wild carrot. Is the cause of the 
