OF THE HAWAIIAN ARCHIPELAGO 487 
The internodes become shorter and the plant more condensed as the intensity of 
the light increases, while the leaves attain their maximal size at a certain medium in- 
tensity of illumination. This latter is owing to the fact that moderate light stimu- 
lates the growth of the leaves, whereas intense light retards it 
Jost (’07, p. 125) makes the following statements: 
are not accurately acquainted with the precise way in which assimilation is 
light; it is questionable, however, whether this is the rule with higher intensities . . . 
may be easily imagined that a further increase in assimilation, following on in- 
crease in light, is impossible owing to the deficiency in carbon-dioxide. Carbon- 
dioxide may be present in sufficient quantity under ordinary circumstances to em- 
ploy all the energy of sunlight, but when light is aNd increased the usual 
amount of carbon dioxide would constitute a sub-optim 
Schimper (’03, p. 58) states as a result of excess 2 aye 
£ éhai 
Terrestrial plants . . . frequently suffer f a Ee ae 
chlorophyll. The veemasion of very sunny spots is never pure grea; but always 
exhibits an admixture of yellow and brown tints due to the products of decompo- 
intense tropical light may even completely bleach the 
sition of chlorophyll... 
foliage. 
Many of the Hawaiian beach plants are grayish or yellowish 
green. This is characteristic, not only of Hawaii, but also of other 
strands. As Cockayne (’11) aes 
The yellow colour of 
is doubtless correlated 
heredity of an acquired character. 
The author cannot share the latter view, as beach plants which 
have happened to grow in the shadedevelop normal green pigment, 
instead of the bleached beach pigment. Such species as Santalum 
Freycenetianum var. littorale, Lepidium owathense, Euphorbia 
cordata, Batis maritima, Argyreia tiliaefolia, and Cressa cretica fur- 
nish excellent examples of this pronounced difference between the 
sun leaves and shade leaves of littoral plants. 
A further comparison may be made which will illustrate the 
intensity of the strand illumination. In the rain-forest and 
summit-bog zones, and in the deep ravines of the lower and middle 
forests, the ordinary illumination on cloudy days—and these are 
regions of almost continuous cloudiness—necessitates a photo- 
graphic exposure of say three minutes, whereas the same subject, 
distance, and aperture on the strand would require but one 
seventy-fifth of a second. The difference in illumination indi- 
ey L 43 or es sae 
with excess of ‘light, onde seems to me a possible example of 
