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PACIFIC SCIENCE, Vol. XI, April, 1957 
since it lacks trichomes on both mature leaves 
and peduncles . Hesperomannia arborescens shows 
intermediate stages, since uniseriate hairs are 
present on peduncles, though lacking on 
mature leaves. Biseriate glandular trichomes 
have likewise disappeared from mature leaves 
in some populations of this species. 
The involucral bracts of H. Lydgatei may be 
interpreted as advanced in their structure. 
Likewise, the lack of median veins in corolla 
lobes of this species, despite optimal lobe- 
width, would seem to be an advanced char- 
acteristic. Absence of median veins in flowers 
of H. arborescens subsp. arborescens and subsp. 
Bushiana may similarly be interpreted as re- 
ductions, if the generally-accepted tenet of 
Koch (1930: 940) that median veins are 
primitively present in the family is correct. 
Thus, H. arbuscula would seem to possess 
the more primitive characteristics. Hesperoman- 
nia arborescens shows somewhat more ad- 
vanced features, while H. Lydgatei is differ- 
entiated from the other species by characters 
which seem best interpreted as the most ad- 
vanced condition in the genus. 
SYSTEMATIC TREATMENT AND DISCUSSION 
The writer has had the privilege of studying 
type or isotype material of all of the species 
of Hesperomannia. In addition, the collections 
of the three largest assemblages of specimens 
of this genus, those of the Bishop Museum, 
the Gray and Arnold herbaria at Harvard, and 
the Herbarium of the University of California, 
Berkeley, have been examined. This com- 
paratively large amount of material has per- 
mitted a more comprehensive picture of spe- 
cies variability than has previously been 
available. The descriptions of Degener (1946) 
are adequate for indicating some of the ex- 
tremes of variation, particularly in the com- 
plex recognized here as H. arborescens. These 
descriptions do not incorporate the interme- 
diate expressions of characters that are found 
in many specimens, however, and the dis- 
cussions following each of the taxa below 
emend these descriptions where necessary, 
suggesting the most constant characters for 
each taxon recognized. 
KEY TO SPECIES AND SUBSPECIES 
IA. Peduncles 1.8 mm. in diameter or less, 
glabrous; inner involucral bracts 3.5 to 
5 cm. long; corolla lobes without diffuse 
sclereids H. Lydgatei 
IB. Peduncles 3 mm. in diameter or more, 
bearing hairs even at maturity; inner in- 
volucral bracts 3-3 cm. long or less; 
corolla lobes with diffuse sclereids in 
subepidermal layers 2 
2A. Leaves elliptic, the lamina base acute; 
abaxial surface of mature leaf covered 
with numerous uniseriate sclerified hairs 
3. (H. arbuscula) 
3A. Straggling shrub; hairs on abaxial sur- 
face of leaf relatively sparse; diffuse 
sclereids in corolla lobes infrequent; 
West Maui 
H. arbuscula subsp. arbuscula 
3B. Tree; abaxial surface of leaf densely 
coated with hairs; numerous diffuse 
sclereids present in corolla lobes; Waia- 
nae Mts., Oahu ' 
H. arbuscula subsp. oahuensis 
2B. Leaves lanceolate to oblanceolate or ob- 
ovate, the lamina base acuminate; no 
uniseriate hairs present on mature leaves 
4. (H. arborescens) 
4A. Achenes at maturity 12-14 mm. long; 
no median corolla veins present; Lanai 
. ,H. arborescens subsp. arborescens 
4B. Achenes at maturity 12 mm. or less in 
length; median corolla veins present or 
not; Koolau Mts., Oahu. 5 
5A. Heads solitary or in clusters of 2 to 10; 
heads containing 30 or more flowers; 
median veins present in some corolla 
lobes. .H. arborescens subsp. Swezeyi 
5B. Heads solitary, containing approximate- 
ly 25 flowers; no median veins in corolla 
lobes . H. arborescens subsp. Bushiana 
