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1917] MacCAUGHEY—HAWAIIAN FLORA 415 
Acacia Farnensiana, Amaranthus spinosus, Argemone mexicana, 
Caesalpinia Bonducella, Cyanea solanacea var. quercifolia, Rubus 
hawatiensis, Sida spinosa, Solanum incompletum, Opuntia tuna, 
Lantana camara, and Prosopis juliflora are representative plants 
of this class (fig. 22). 
FOLIAGE MINUTE OR SCALELIKE, or showing strong xerophilous 
modification.—Acacia koa and A. koaia (phyllodia), Exocarpus 
Gaudichaudii, Portulaca sclerocarpa, Silene struthioloides, and 
Sityphelia spp. are examples of very small foliage. Cassytha- 
jiliformis and Viscum articulatum, two parasitic plants, have 
minute or vestigial leaves. 
Drcimpuous HABIT.—The deciduous habit is quite rare among 
Hawaiian plants, either in the rain forest or on the lava fields. 
Only 3 deciduous species occur on the lava flows, namely, Erythrina 
monosperma, Sapindus saponaria, and Reynoldsia sandwicensis. 
DECUMBENT, STRAGGLING, OR VINELIKE HABIT.—A very large 
number, nearly 60 in all, or 33 per cent, of the lava flow plants are 
either habitually prostrate or decumbent, or assume these growth- 
forms on the lava. Genera containing representative species of 
these habits are Abutilon, Argyreia, Boerhaavia, Caesalpina, Cap- 
paris, Cassia, Chenopodium, Cocculus, Embélia, Euphorbia, Fragaria, 
Gossypium, Ipomoea, Lepidium, Lipochaeta, Meibomia, Mucuna, 
Osteomeles, Plumbago, Portulaca, Raillardia, Ranunculus, Rubus, 
Rumex, Scaevola, Sicyos, Sida, Solanum, Stenogyne, Styphelia, 
Tetramolopium, Vicia, Vigna, and Wikstroemia. Compact basal 
heads or rosettes are formed by such plants as Argyroxiphium 
spp., Gnaphalium spp., Plantago pachyphylla, Sisyrinchiwm acre, 
Sonchus, etc. 
SuccULENCE.—This typical xerophytic character is relatively 
uncommon in the lava flow flora. The few examples are mostly 
introduced weeds, as Portulaca,Opuntia, Bryophyllum, C heno podium, 
Sonchus. Lignescence, representing the other extreme of struc- 
tural adaptation to aridity, is the dominant condition. - 
HiGH PERCENTAGE OF LIGNEOUS FoRMS.—Upon examining a 
tabular statement of the habital characters of the lava flow flora, 
one is immediately impressed by the high proportion of ligneous 
and semi-ligneous forms. Over 70 per cent are woody, and this 
