VEGETATION OF HAWAIIAN LAVA FLOWS 
VAUGHAN MAcCCAUGHEY 
(WITH TWENTY-TWO FIGURES) 
Introduction 
This paper is a survey of the more important types of vegetation 
which occur on the lava fields of the Hawaiian Archipelago and 
their ecological relations. It has particular reference to the sper- 
matophytes, as our taxonomic knowledge of the native land algae, 
lichens, bryophytes, and pteridophytes is still in a somewhat 
fragmentary and unsettled condition. The scope of the paper 
is further restricted by including only the arid or xerophytic dis- 
tricts where the lava flows are relatively barren. Under humid 
climate the flows rapidly disintegrate into rich volcanic soil and 
support a luxuriant rain forest. This paper is concerned with the 
ecology of the xerophytic regions, as these have largely been 
neglected in the literature of Hawaiian botany. 
There is a widespread association of ideas which couples tropical 
with humid conditions, due no doubt to the many semipopular 
accounts of the “tropical jungle” and to the types of vegetation 
usually exhibited in the northern conservatories. It requires a 
distinct readjustment of perspective to realize that many tropical 
regions possess large areas of extreme aridity. The Hawaiian 
Archipelago, situated just within the tropics in the center of the 
North Pacific Ocean, admirably illustrates this condition. Most 
of the popular and semitechnical accounts of the islands have 
emphasized the beautiful humid woodlands and have either ignored 
or given scant attention to the vast rocky waste lands of barren 
lava flow and cinder field. 
It has been the writer’s privilege, during a residence of 8 years 
in the islands, to have made many expeditions into these arid 
regions and to have ascended all of the high mountains of the 
group. This paper is an outgrowth of these trips, some of which 
have occupied many weeks. In order to make clear the ecological 
Botanical Gazette, vol. 64] [386 
