The Subgenera of Dubautia (Compositae) : Hawaiian Plant Studies 18 1 
Harold St. John 2 
THE SUBGENERA OF Dubautia 
The shrubby or arborescent Compositae of 
the Hawaiian Islands have attracted much 
attention and study. Among them are the 
related genera Dubautia and Railliardia, early 
described by Gaudichaud and maintained by 
nearly every investigator to the present. They 
were separated by characters of the involucre, 
paleae, and pappus. Many of the botanists 
who have done field work in Hawaii got their 
first concept of Dubautia from D. plantagi- 
nea, a vigorous small tree of the mountains 
of Oahu. Its involucre of 4 to 6 firm distinct 
bracts and its terminal plume of crowded 
oblong-oblanceolate leaves, glabrate on the 
surfaces, give it a very marked habit and as- 
pect. In Railliardia there are numerous spe- 
cies — small bushes with sessile and coriace- 
ous, often decussate, leaves which clothe the 
stem for a considerable distance. The involu- 
cre is cylindric or campanulate, of several in- 
volucral bracts united into a tube. Once 
formed, it is difficult to break away from this 
concept of the two old genera, but R. arborea 
Gray and R. struthioloides Gray are trees; 
and R. lonchophylla Sherff, though a shrub 
x This is the eighteenth of a series of papers de- 
signed to present descriptions, revisions, and rec- 
ords of Hawaiian plants. The preceding papers 
have been published in Bernice P. Bishop Mus., 
Occas. Papers 10(4), 1933; 10(12), 1934; 11 
(14), 1935; 12(8), 1936; 14(8), 1938; 15(1), 
1939; 15(2), 1939; 15(22), 1940; 15(28), 
1940; 17(12), 1943; Calif. Acad. Sci., Proc. IV, 
25(16), 1946; Torrey Bot. Club, Bui. 72: 22-30, 
1945; Lloydia 7: 265-274, 1944; Pacific Sci. 1: 
5-20, 1947; Brittonia 6(4): 431-449, 1949; 
Gray Herb., Contrib. 165: 39-42, pi. 3, 1947; 
Pacific Sci. 3(4) : 296-301, 1949. 
2 Chairman, Department of Botany, University 
of Hawaii. Manuscript received November 22, 
1949. 
only 3 to 4 feet tall, has foliage similar to 
that of D. plantaginea. Thus, if all the known 
species are examined, it is evident that there 
can be no consistent groupings of the species 
into several genera on the basis of stature, 
foliage, or involucre. 
In a review of Dubautia and Railliardia, 
Keck (1936: 24-25) emphasized the exist- 
ence of species invalidating each one of the 
several characters alleged to separate the two 
genera. The two genera had recently been 
monographed, but Keck asserted (p. 25) that 
the monographer ’'Sherff gives an admirable 
systematic account of the species, but evades 
the question of how the two genera are to 
be distinguished by failing to raise it.” 
To one acquainted with the plants in the 
field there is no habital aspect to separate the 
species into two groups and, as indicated, 
there are no strong morphological differ- 
ences, not even a single constant character. 
Keck’s merging of the two genera has not 
been generally adopted, inasmuch as the fol- 
lowing botanists have continued in the main- 
tenance of both Dubautia and Railliardia: 
Sherff (1941: 29-30); Degener (1940 and 
1946); and Selling (1947: 330-332), who 
gave the first detailed account of the pollen 
of the Hawaiian plants. Selling accepted both 
Dubautia and Raillardia { —Railliardia} , and, 
referring (p. 331) to Keck’s reduction, said 
"there seems to be no proper reason for this.” 
Selling describes and illustrates pollen of the 
two genera, describing it in almost identical 
phrasing. He states that one cannot separate 
Railliardia from Dubautia on the basis of 
structure of the pollen grains. This might 
sound like a significant fact, but also insep- 
arable on the basis of pollen structure, are the 
C 339 } 
