MACFARLANE: SYNCHRONISM IN PLANT STRUCTURES 319 
26, and in wonderfully exact and graded succession, with definite time 
interval between each, later flowers open along the elongating axis. 
But just three days before, or on June 23, the central flowers of the 
cymes on our common Indian bean (Catalpa bignonioides) expand, and 
for about 16 days thereafter successive blooms open in exact ratio, if 
weather conditions are favorable. But a decided retardation may 
occur, if cold winds and wetting rains interfere. 
We would draw attention now to some cases of synchrony in floral 
parts. From the time of Linnaeus onward descriptions of floral clocks 
have been frequent, and no matter what value we attach to such, the 
very device points to a surprisingly exact time during the twenty-four 
hours when the blooms of each species open. But the maturation and 
opening of each flower, as well as the behavior of such parts as the 
stamens and styles of it, may vary according to the degree of thermic 
energy, or lumic energy, or both that act on these. Such variation 
seems to explain apparently contradictory results that have been 
recorded by different botanists. Thus Kerner’s attractive state- 
ments® regarding Silene nutans and its successive maturation of one 
row of stamens in each flower, on one evening, of a second row on a 
succeeding evening, and of the styles on the third, have called forth 
adverse comment along with the statement that no such exact suc- 
cession occurs. But first about twelve years ago along the Trafoi 
Ravine in the Tirol, and nearly seven years ago by Morgarten Field 
in Switzerland, the writer was able to prove that both statements 
might apply according to environal conditions. For when the days 
and nights in August are warm, with clear sky overhead, the exact 
succession noted by Kerner can readily be traced. But if the days, 
and even: more the nights, be cold, raw and at times accompanied by 
rains, then a nearly simultaneous maturation of all ten stamens and 
at times even of the styles may occur. 
_ By careful observation, however, during warm dry days we were 
able to determine an even more exact and synchronous behavior of the 
ten stamens than that noted above. For on the first evening from 
about 6 to 7.30 the anthers of the earlier 5 stamens matured in circular 
succession with a clear time interval between each, and then were ready 
to scatter pollen; while on the succeeding evening, the second five 
ripened similarly. Such again calls to mind the time period shown in 
maturation of the five anthers on the stamens of the giant cow parsnip 
(Heracleum lanatum). It was found even that the dropping of the 
anthers in Silene mentioned by Kerner takes place not together, or 
irregularly, but in correlated succession if environal stimuli are favor- 
3 Nat. Hist. of Pl. 2, p. 154. 
22, 
