1917] MAcCAUGHEY—HAWAIIAN FLORA 417 
it especially typical of them. A very large proportion of the indi- 
genous vegetation in the humid forests is shrubby or arborescent. 
In the Hawaiian Islands woodiness is to be interpreted, not 
as a xerophytic feature, but rather as a result of long continued 
plant growth (in terms of the individual plant) under unfavorable 
conditions. The low temperatures and excessive humidity of the 
rain forest belt are probably just as unfavorable for optimum plant 
growth as are the high temperatures and excessive aridity of the 
lava fields. Both habitats result in the production or modification 
of a large number of very lignescent, suffruticose, dwarfed, slow 
growing species (tables I and II). 
TABLE I 
HABITAL ANALYSIS OF THE LAVA FLOW FLORA 
Class | Frequent | Rare | Total 
EPOCH Nace ees 48 Io 58 
eS Gg oni ele 65 2 67 
Herbaceous perennials 29 4 33 
ANDURIE G3 25a 3 24 2 26 
TABLE II 
ENDEMICITY AND LIGNESCENCE OF LAVA FLOW PLANTS* 
Not endemic | Total 
Class Endemic 
Woody throughout. . go 108 
Partly woody.....-.. 28 10 38 
Herbaceous......... 12 24 36 
ROME ccieerveswes | 130 §2 | 182 
pes. 5 bo ber vg io" oe che total lave ow Hora is tomposed of woody 
and partly Lal age we 
Roor sysTEMS OF LAVA FLOW PLANTS.—No comprehensive 
data are available on this interesting subject. The observations 
of the writer would tend to point to the comparatively deep rooted- 
ness of the woody species. The aridity of the flows has already 
been described. Deeply penetrating roots may be considered as 
absolutely essential for the existence of perennial plants on a rocky 
stratum as dry as the typical lava flow. The roots of such species 
