OF THE HAWAIIAN ARCHIPELAGO 493 
this vegetation is distinctly adjusted to the physical conditions, 
for it is of great paucity, of small and slow growth, annually re- 
newed, closely ground-appressed, and strongly xerophytic.”’ 
Brownlie (’02) makes much of the irregularity of the tidal 
intervals in the Pacific, and states that at Honolulu the intervals 
of time from one high water to the next vary from ten and three- 
quarters to thirteen and three-quarters hours. A range so wide 
apart shows great irregularity compared with the absolute regular- 
ity of the movements of the moon. Although this tidal phenome- 
non is of great significance from the standpoint of tide studies 
themselves, it is not a factor of any special importance in the lit- 
toral ecology of land-plants. 
Although the Hawaiian marine flora is closely limited by tidal 
intervals, these intervals are of little significance in determining 
the zonation of land-plants, as compared with the importance of 
other ecological factors. This contrasts with the findings of John- 
son and York (’15, p. 149), at Cold Spring Harbor, who state: 
ft tical distributi f the littoral plants about this harbor 
careful study OL he v 
shows that this depends primarily and very definitely on the relative time of their 
b d ith the ri d fall of the tide. Moreover, the vertical 
range of littoral species is strictly, sometimes very narrowly limited. There are no 
algae, that are distributed “ between tidemarks”’ 
: fe rted 
species here, except two or three 
e nearest approach 
(i. e., from low water up to high 
this range found for any seed pla 
It must be noted that the above statement uses the term littoral 
in a relatively narrow sense, as does their further statement that 
the vertical range of a littoral plant is exactly proportional to the 
range of the tide. This does not apply to the customary usage of 
the term littoral, which includes all vegetation along the coasts or 
strands, the ranges of which are more or less closely maritime. 
ter 
nt is that of Spartina glabra. 
NATURE OF THE SUBSTRATUM 
The character of the littoral substratum obviously plays an 
important rdle in determining the nature and distribution of the 
littoral flora. Warming (’09, p. 223) groups halophytic plants 
into four classes, according to the nature of the substratum upon 
which they reach their optimum development: lithophilous, 
psammophilous, pelophilous, and helophilous. This will serve asa 
convenient basis for classifying the Hawaiian strand, with the 
