OBSERVATIONS ON THE CAUSES OF GREGARIOUS 
FLOWERING IN PLANTS 1 
William Seifriz 
(Received for publication May n, 1922) 
One of the most interesting and fundamental of biological problems is 
that of the extent to which the life processes of an organism are influenced 
by the external environment. In the past, biologists have been quite 
content to rest secure in the belief that the most deep-seated characters in 
organisms are developed in the individual and transmitted from one genera¬ 
tion to another little influenced, and certainly not determined, by the ex¬ 
ternal environment of the organism. That so fundamental a character as 
paired eyes in vertebrates could in any great degree be influenced by a 
change in external environment was hardly conceivable until Stockard 
showed that if the eggs of the fish Fundulus are placed in sea water to which 
a little magnesium chloride has been added they develop into embryos 
with one medium cyclopean eye. 
Equally interesting to the botanist have been the experiments of Garner 
and Allard (6), who were able by controlling the time of exposure of a 
plant to light greatly to lower or increase the age at which the plant reaches 
sexual maturity. Thus, the field aster, which commonly requires four 
months (May to September) to reach sexual maturity, was made, by 
decreasing the time of exposure to daylight, to bear flowers within a month 
after germination (by June 18). Still more remarkable is the fact that 
these same plants, instead of completing their life cycle by dying after 
flowering, as they would have done in the field, developed new axillary 
branches (on being restored to normal light exposure) and flowered a second 
time in September. 
It is thus evident that certain characters of a deep-seated and fundamental 
nature which heretofore have been regarded as immutable, are relatively 
unstable and respond readily to changes in the external environment. It 
is, consequently, not surprising that some biologists hold that all '‘characters 
are of the nature of responses to environment” (7, p. 530), and that “every 
life process must to some degree be dependent upon the external world” 
(15, p. 285). 
While it is difficult to deny the truth of these statements in the face of 
the remarkable experiments which have been performed, yet one wonders 
how far such a theory will carry us. We hesitate to admit that the external 
environment is in any way responsible for the fact that a pine seed develops 
1 Contribution from the Osborn Botanical Laboratory. 
93 
