g8 AMERICAN JOURNAL OF BOTANY [Vol. 10, 



The sexual cycles of D. arundinacea and D. stricius are about thirty-two 

 years in length. Bambusa polymorpha is known to have a very long life 

 period. I know of no authentic record of two successive flowering dates. 



In the Indian Forester for 1903 appears the statement that "the last 

 recorded flowering of the Kyathaung was ... in 1853" (13, p. 244). The 

 flowering of this bamboo, Bambusa polymorpha, was expected to recur 

 shortly after 1883 on the general belief that the life of bamboos is about 

 thirty years. The flowering of B. polymorpha in the forests of Burma has 

 not yet occurred. Certain "signs" of an expected flowering have from 

 time to time been seen. These signs refer to the well-known habit which 

 bamboos have of producing no new shoots in the year of flowering. 



The bamboo forests of B. polymorpha in Burma may be reckoned by 

 hundreds if not by thousands of square miles. In this extensive region of 

 bamboos there have been, since 1883, one or two false alarms of gregarious 

 flowering when a clump or two has blossomed. In 1918 and 1919 an area 

 of several hundred acres in two or three distinct but neighboring blocks in 

 the Tharrawaddy Division flowered gregariously .? (The plants of B. poly- 

 morpha were at this time sixty-five years of age.) This was thought to be 

 the forerunner of a general flowering, since the flowering of odd clumps is 

 considered to be an indication that the flowering of the whole area is im- 

 minent. But so far no general flowering has taken place. 



During their sixty-eight years of existence the bamboos of these forests 

 have endured many droughts which apparently have had no effect whatso- 

 ever on the sexual maturity of the plants. For at least the latter half of 

 their life the bamboos must certainly have been mature enough to respond 

 to an external stimulus, if this stimulus is of such a nature as to exercise 

 any prominent influence on the sexual life of the plants. 



We have so far seen, first, that bamboos of long and rhythmic life 

 cycles reach sexual maturity when experiencing only the normal annual 

 dry season of the tropics ; and second, that other bamboos of long periodicity 

 have for sixty-eight years failed to attain sexual maturity even though they 

 have experienced many seasons of both normal dry weather and drought. 

 There now remain to be considered those instances in which flowering takes 

 place in the entire absence not only of drought but even of a typical tropical 

 annual dry season. 



The most striking instance of this is the behavior of the bamboos at 

 Buitenzorg, Java, where droughts are unknown and dry seasons are few 

 and far between. Before passing on to the Buitenzorg data it will be 

 interesting to consider in more detail the similar case of the climbing bam- 

 boo, Chusquea abietifolia, already referred to. This bamboo, a slender 

 scandent form, occurs in great abundance throughout the mountains of 

 Jamaica. The high altitude regions of Jamaica receive abundant moisture 



4 I am indebted to H. R. Blanford, Esq., O. B. E., Government silviculturist at May- 

 myo, Burma, for this information. 



