Jan., 1923] SEIFRIZ — GREGARIOUS FLOWERING 37 
responds to the first stimulus and produces blossoms on the first flowering 
day, it does not respond to the second stimulus and is bare of blossoms on 
the second flowering day when other shoots of the same plant are in flower. 
Whether or not we are near an accurate knowledge of the precise mech¬ 
anism involved, it seems safe to conclude: first, that simultaneity in the 
flowering of the orchid Dendrobium crumenatum is the expression of an 
innate, heritable factor; and second, that the exact time at which this 
simultaneous flowering shall take place is determined by an external environ¬ 
mental factor occurring eight days in advance of the flowering date. The 
precise nature of this environmental stimulus is not irrefutably established. 
If it is not heavy rainfall it is certainly a factor commonly associated 
with rainfall. 
BIBLIOGRAPHY 
1. Brandis, D. Indian trees. An account of trees, shrubs, woody climbers, bamboos and 
palms indigenous or commonly cultivated in the British Indian Empire. London, 
1906. 
2. Kawamura, S. On the cause of flowering of bamboo (Japanese). Bot. Mag. Tokyo 
25: 237-269. 1911. Abstr. in Zeitschr. Pflanzenziicht. (Fruwirth) 1: 96. 1913. 
3. Seifriz, W. The length of the life cycle of a climbing bamboo. A striking case of 
sexual periodicity in Chusquea abietifolia Griseb. Amer. Jour. Bot. 7: 83-94. 1920. 
4. Schimper, A. F. W. Plant geography (Eng. transl.). Oxford, 1913. 
5. Rutgers, A. A. F., and Went, F. A. F. C. Periodische Erscheinungen bei den Bliiten 
des Dendrobium crumenatum Lindl. Ann. Jard. Bot. Buitenzorg II, 14: 129-160. 
1916. 
6. Burkill, I. H. The flowering of the pigeon orchid, Dendrobium crumenatum. Gardener’s 
Bull., Straits Settlements 1: 400. 1917. 
