Feb., 1923] 
SEIFRIZ — CAUSES OF GREGARIOUS FLOWERING 
95 
That bamboos have flowered gregariously in India immediately after a 
drought is not to be doubted. Droughts are of such frequent occurrence 
in India that it would be surprising if they did not occasionally coincide 
with the flowering of bamboo forests. It is also possible that severe dry 
weather may have some slight influence on the exact time of flowering. 
When many individuals of a species flower simultaneously immediately 
after a drought, scientist as well as layman is likely to associate the two 
phenomena. The occurrence of each phenomenon separately passes un¬ 
noticed. But even if our data should warrant the conclusion that the 
gregarious flowering of a particular species is occasioned by drought in a 
certain locality, what are we to do with the fact that the same species 
flowers in another locality where there is no drought? Bambusa arundinacea, 
for example, flowers not only in India, where it is subjected annually to a 
severe dry season and occasionally to a drought, but also in Buitenzorg, 
Java, where dry seasons are practically unknown. Then, too, we have the 
interesting fact that other species of bamboo flower gregariously following 
an unusually wet period, as did, for example, the climbing bamboo, Chusquea 
abietifolia , in Jamaica in 1918 (20). Still other bamboos show no periodic¬ 
ity at all and flower sporadically without any apparent relation to climate. 
This is true of the Philippine bamboos in general, among which no case of 
simultaneous flowering of many individuals is known, although these 
bamboos have been under scientific observation for nineteen years. 2 
So far as I have knowledge, no one has actually investigated the rain¬ 
fall data of the country where bamboos flower gregariously in order to 
ascertain, first, whether or not the dry season of the particular year in 
question was one of sufficient severity to warrant its being regarded as the 
direct cause of the gregarious flowering of the bamboos; and, second, 
whether or not, in case a drought did precede the particular flowering 
period under investigation, other flowering periods of the same species 
of bamboos in that country (and in other countries) were also preceded 
by droughts. 
The meteorological conditions prevailing in India are so extreme that 
one must be thoroughly aware of them in order to investigate intelligently 
a question such as that under consideration. The greater part of India is 
almost rainless for about seven months of the year. It is not an uncommon 
occurrence for no rain whatever to fall at certain stations during eight 
months of the year. The absence of rain during such a normal dry season 
cannot, of course, in any sense be regarded as a drought. What rain does 
fall during the dry season (averaging 0.2 to 0.3 of an inch a month) is of 
little consequence to plant life. Vegetation depends solely on the mon¬ 
soons, which occur from June to September in Hyderabad and the Central 
Provinces, for example, and from October to December in Southeast 
2 Dr. E. D. Merrill, Director of the Philippine Bureau of Science, has kindly given me 
this and other valued information. 
