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. 



