344 SEMI-CENTENNIAL OF TORREY BOTANICAL CLUB 
averaged 15.1, 149 laterals only 11.1. In both years the maximum 
for terminals was 13, a number of the Fibonacci series, that for 
laterals 11, a number of the Trientalis series. More intensive 
studies were made of partial variability in one plant of Eupatorium 
album. ‘This species has only tubular flowers and the counts were 
hence made of the total flower number. The plant studied had 
six branches. On each branch Vogler counted the terminal heads, 
and then the laterals in succession downward. The most notice- 
able points brought out by his data are that the flower number is 
different for the various main branches and that on the same 
branch the number is different for terminals and laterals, especially 
for branches near the top of the plant. 
А survey of Vogler's work shows that the maxima do not always 
accord with the series of Fibonacci; they may fall on other numbers 
such as certain of the Trientalis series. He has also observed and 
emphasized the significance of partial variability, which he views 
as evidence against the conception that rhythmic divisions give 
harmony between mother and daughter organs as to position and 
number. 
IV. EVIDENCE OF INTRASEASONAL VARIABILITY 
Some interesting observations regarding intraseasonal varia- 
bility in number of flowers per head are reported by MacLeod 
(99). He found that the ray- and disk-flowers of Centaurea 
Cyanus, C. alba, and C. atropurpurea, whether from terminal or 
from lateral heads, are more numerous per head early in the season 
than later. However, as he studied heads indiscriminately, there 
are no data on the individual behavior of plants. He grew some 
of his plants on poor and some on rich soil and found that those 
on poor soil had a lower flower number per head than those on 
rich. He rightly points out that experimental breeding work of 
this kind is necessary in order to determine whether differences 
are due to heredity or merely to food supply and season. 
Tower ('o2) reported differences in flower number for heads 
of Chrysanthemum Leucanthemum collected in the same location, 
but at different dates (July 5 and 30) of the same season. When 
grouped, such data gave a bimodal curve involving what he calls 
"secular modes.” 
