Feb., 1923] SEIFRIZ CAUSES OF GREGARIOUS FLOWERING IOI 



inches of rain as compared with a normal average of 21.95 inches for this 

 period. Especially trying must this drought have been on plant growth in 

 view of the fact that the precipitation in April, which usually ends the 

 normal dry season, was less than half the average, while in May there fell 

 but 0.75 inch of rain as compared with a normal precipitation for this 

 month of nearly five inches (4.90). In 191 1 the talipot palms were but 

 seven years younger than in 1918, i.e., they were thirty years old, not too 

 young to respond sexually to an external stimulus of some force. 



Through all these droughts the six talipots, with others in the Peradeniya 

 Gardens and hundreds throughout Ceylon, the twenty clumps of bamboo, 

 and the liane Bauhinia, grew on without flowering. It is therefore hardly 

 likely that the relatively mild drought of 19 18 had any influence on the 

 flowering of these plants. 



The second objection to be raised against the conclusion that drought 

 caused the flowering of the plants in the Peradeniya Gardens is that nine 

 out of the sixteen talipot palms did not flower, and these nine were of the 

 same age and had been growing under the same conditions as the seven 

 which did flower. Obviously, if flowering was the direct result of drought 

 or of any other climatic factor, the seven palms which were affected must 

 have been in such a physiological state as to be susceptible to the influence 

 while the other nine palms were not in such a state. That is, if drought is 

 a factor it is a secondary one, the physiological condition of the plant being 

 the primary determining factor. 



If we conclude that the ultimate cause of the time of attaining sexual 

 maturity lies in the hereditary disposition of the plant, the interesting 

 question arises, Why did seven of the talipots flower and nine not, since all 

 in the avenue were of the same age? We can only attribute this difference 

 in behavior to individual differences in the germ plasm, concerning the 

 causes of which we know nothing. The age at which Corypha umbraculifera 

 reaches sexual maturity is not the same in all individuals. 



The final and most convincing evidence against the hypothesis that 

 drought is the direct cause of flowering, or even a factor of any great signifi- 

 cance in the flowering of certain palms and bamboos, is the behavior of 

 another talipot at Peradeniya and of a talipot and the bamboos at Buiten- 

 zorg. The talipot in question at Peradeniya is one which flowered some 

 years ago, in 1903 (fig. 2). For four years (1899-1902) previous to the 

 flowering of this palm at Peradeniya the average annual rainfall was, in 

 each of these four years, above the normal average. In 1902, the year 

 immediately preceding the flowering, the total annual rainfall was approxi- 

 mately one third above the normal average. It is quite evident that the 

 flowering of this talipot can in no way be attributed to drought. 



When the many talipots in Ceylon were blossoming in 1918, the only 

 old specimen of this palm in the gardens at Buitenzorg was also in flower 

 (fig. 3). At Buitenzorg there is no such thing as drought. The writer was 



