LENGTH OF THE LIFE CYCLE OF A CLIMBING BAMBOO 93 
present seasonal factors is to be had from the behavior of the dimbing bam- 
boos sent to Kew. Morris (5) himself presents a bit of evidence against 
his own contention when he says, "Both the wild plants at Jamaica and the 
cultivated plants at Kew (although the latter were under such very different 
conditions) were in flower at the same time." 
Should the life cycle of Chusquea ahieiifolia prove not to vary from the 
thirty- three years which it has been found to be — just as the cycle of 
Bamhusa arundinacea has, from three successive observations (1804, 1836, 
1868) been found to be exactly thirty- two years (i) — then it would seem 
hardly likely that the length of this term of years could be definitely ascribed 
to present climatic influences, unless there is some larger climatic round 
of years, such as that suggested by Bruckner (9). 
It is interesting to note, though of how much significance this may be 
is pure conjecture, that the climatic oscillation ascertained by Bruckner 
(9) closely approaches in length of years the life cycle of Chusquea. There 
is, however, in addition to Bruckner's 35-year alternation of wet and dry 
epochs, a supposed variation of rainfall in a cycle of eleven years, coinci- 
dently with the sunspot cycle (10) . It is as yet by no means well established 
that climatic changes are periodic, and there is but little to support the idea 
that droughts occur rhythmically, especially with any great precision. 
In considering the possible relationship between sexual periodicity in 
plants and climatic oscillations I have had in mind — as I assume others 
have had in their attempts to associate the two — only present climatic 
influences. That past rhythmical variations in rainfall or in temperature 
have, through the ages, fixed the life-cycle of Chusquea is quite possible. 
So striking is the association between the life of an annual and the seasons 
that it seems very probable indeed that the cycle of annuals is the direct 
result of seasonal influences, and that this cycle has, through many gener- 
ations, become so firmly established as to be unalterable through the tem- 
porary elimination of seasons by transferring the annual to a greenhouse. 
This problem can, however, and should, be attacked from other view- 
points than the purely ecological one. Other factors than such external 
stimuli as droughts and similar seasonal epochs may have been at work in 
establishing, or still are at work in maintaining, sexual periodicity in Chus- 
quea. The problem may be of the same nature as that of puberty and 
senility in organisms. We know, for example, that certain organisms re- 
quire a certain number of years in which to reach sexual maturity, and we 
know that certain organisms live about so long and never exceed a certain 
maximum. The present causes of such phenomena are not as yet seriously 
thought to be environmental in nature. That they may be somewhat in- 
fluenced by environment is possible. Lack of food, for example, is said to 
hasten the attaining of sexual maturity in man, but the digression from the 
mean is slight and has no direct bearing on the original establishment of 
the phenomenon. 
