Rutaceae. 
arrangement are not at all well brought out in the Hawaiian species. In most 
of the other works Engler’s new combinations have been placed as synonyms. 
The genus Xanthoxylum is distributed over North America, Eastern Asia and 
also most tropical countries. It is found in Polynesia, outside of the Hawaiian 
Islands, where seven species and numerous varieties have so far been discovered, 
only in Tahiti. All Hawaiian species are unarmed. The leaves are quite aro- 
matic, most of them having a peculiar soapy odor, while one, Y. hawaiiense Hbd. 
var. citriodoro, is strongly lemon-scented. The flowers of some species are also 
quite fragrant. 
Most of our Xanthoxyla inhabit the dry regions on the leeward sides, espe- 
cially old lava flows, where they reach their best development, as, for example, 
on the southern slopes of Mt. Haleakala, Puuwaawaa, North Kona, Hawaii, and 
on Mauna Kea in the open serub-country. Several species oceur only in the rain 
forests, as XY. oahuense and X. Bluettianum. They are usually found at an ele- 
vation of 2500 to 4000 feet, but rarely higher. All Hawaiian Xanthoxyla are 
trees, except a new species found in the Kohala rain forests. 
KEY TO SPECIES. 
Petals 4, thin ne vp aan imbricate. Flowering panicles appear before the leaves in the 
se 
sir of larg 
eaflets hess ternate, the lateral ones on long petiolules. 
All petiolules arioalee at or below the middle............... x. tescnnoace 
ateral selon olul Aacaenas pelea sets 5 pe Mir ater ee a x. 
eaflet peer neate on petiolules of 16-20 mm.......... be a edna 
Leaflets 7 si 3 oe beh the lateral meric sessile or on ragga petiolules. 
eaflets 9-7 reeshaneng ate with copious oil-dots............-.---- X. glandulosum 
Leaflets 5-3 ovate or ovate oblong ie GWEC cic aceasta eee Kauaiense 
Le = ur 3 or garely 5 , thick, tomentose truncate at the bas X. Mauiense 
Petals 4 or 2, thick coriaceous and valvate. Small stipelliform ieadinta at the base 
of the ‘nee MOREOt ee eae re wes eee he ae Cee eee X. dipetalum 
Xanthoxylum Oahuense Hbd. 
Ae or Heae. 
(Plate 76.) 
XANTHOXYLUM OAHUENSE Hbd. Fl. Haw. ie (1888) 75;—Del Cast. Tl. Fl. Ins. Mar. 
Pae. VI. td, 130.—Fagara Oahuensis Engler in Engl. et Prantl Pfizfam. iI. 
4, (1895) 1 
ree, giakvocs: eiphteg 3-foliolate, on as Lee of 8 to 10 em, their leaflets 
oa 
A small t 
on petioles of near rly even length, the t ermina al o o 8 em, the lateral ones 4 to_ 5 em, 
base, excised in the upper half, glabrous coriaceous, opaque, dark green, ene - 
when dr ce | panicles at the base of the branch 6 to 12 em long, . osely = ew-flowered; 
male flowérs: sepals vailgga petals jereenish, ovoid-oblong blunt at the e 
shy th , stamens sli 2 rd serted 2.5 mm in length, with aie sathate: follicles 
rugose and p or) 
hg sega A’e or Hea’e is a small, rather handsome tree and is peculiar to 
the island after which it is named. It is one of the few Hawaiian Xanthoxyla 
which inhabits the wet middle, or rain forest zone, growing on the highest 
193 
