Feb., 1923] SEIFRIZ — CAUSES OF GREGARIOUS FLOWERING III 



may be true of bamboos of long life cycle, although in this case the climatic 

 factor is apparently no longer active. 



The belief in a germinal factor as the cause of gregarious flowering in 

 bamboos does not imply that this heritable determiner is past being in- 

 fluenced by the external environment. The finding of green specimens of 

 Chusquea abietifolia in the mountains of Jamaica when fully ninety-eight 

 percent of the total number of plants were dead suggests that the usual 

 periodicity of this bamboo has in some individuals become altered. As was 

 pointed out in the introduction of this article, it is the task of the biologist 

 to ascertain to what extent this or that character is susceptible to external 

 influence, i.e., to ascertain the degree of fixity of the innate factor. If it is 

 found that a vital process cannot be altered, then we must admit either 

 that it is too firmly established in the germ plasm to be disturbed, or else 

 that we have not found the requisite environmental factor. This latter 

 assumption is made by Klebs. 



It is impossible to deny the assumption of Klebs that where we are 

 unable to find the controlling environmental factors we have simply failed 

 to search far enough ; yet, until the exact combination of external stimuli 

 is found, the theory that gregarious flowering is determined by a germinal 

 factor stands without disproof.' 



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. Branthwaite, F. J. The flowering of stool shoots of Dendrocalamus strictus. Indian 



Forester 28: 233. 1902. 



3. Burkhill, I. H. The flowering of the pigeon orchid, Dendrobinm crumenatum. Gar- 



dens' Bull., Straits Settlements 1: 400. 191 7. 



4. Ceylon Administration Reports, Dept. of Agr., Annexure V. 1918. 



5. Gamble, J. S. The Bambuseae of British India. Ann. Roy. Bot. Gard. Calcutta 7: 



1896. 



6. Garner, W. W., and Allard, H. A. Effect of the relative length of day and night and 



other factors of the environment on growth and reproduction in plants. Jour. Agr. 

 Res. 18: 553. 1920. 



7. Goodrich, E. S. Some problems in evolution. Science, n. ser. 54: 529. 1921. 



8. Hori, S. On the causes of the flowering disease of bamboos (in Japanese). Bull. Imp. 



Cent. Agr. Exp. Sta. Japan 38: 1. 1911. 



7 After this article was written there appeared an account by Wieland (Amer. Jour. 

 Bot. 8: 218-230. 1921) of monocarpy in the cycadeoids. There is evidence that at least 

 two species of fossil cycads flowered but once in a lifetime. Four other species show a ten- 

 dency toward monocarpy. The most convincing record is that of a specimen of Cycadeoidea 

 Dartoni, the armor of which is packed with hundreds of mature cones. Ample sections of 

 this specimen show no trace of a succeeding foliar crown; although in the very different 

 species, C. ingens, a fine crown of young fronds surmounts a scattered growth of flower 

 buds. It is, therefore, reasonably evident that Cycadeoidea Dartoni was monocarpic. 



It is most interesting to have so authentic a record of monocarpy among the gym- 

 nosperms of past geologic ages. 



