Vegetative Anatomy — Carlquist 
199 
D. Kockii (a single secretory canal 
adaxial to most veins). 
D. Montana (fiber strands near veins 
small). 
D. struthioloides (more nearly isolateral 
than D. Menziesit). 
The different types of leaf structure de- 
tailed above reflect ecological conditions for 
Dubautia to a certain extent, as well as being 
indicative of taxonomic groupings. The thin, 
glabrous leaves of D. Knudsenii, with thin- 
walled epidermal cells, correspond to the 
moist forest areas on Kauai where that spe- 
cies grows. On the contrary, the tendency 
toward thick, isolateral leaves with thick- 
walled epidermal cells in D. Menziesii seems 
related to the dry, sunny alpine habitat of this 
plant. Most of the species indicated here as 
having similarity to D. Menziesii are also 
alpine types. 
The highly specialized leaf anatomy of 
Arg^roxiphium (Carlquist, I9^ld) bears little 
superficial resemblance to that of even the 
isolateral-leaved species of Dubautia. The 
presence of fiber strands along veins, secre- 
tory canals (in A. Caliginii)^ and the presence 
of uniseriate hairs (much more abundant in 
Arg^roxiphium) are similar features. The capi- 
tate biseriate glandular hairs on inflorescence 
bracts of Arg^roxiphium and Wilkesia are very 
similar to those on leaves of Dubautia platy- 
phylla. Dubautia shows little differentiation of 
leaves near inflorescences into inflorescence 
bracts, whereas in Argyroxiphium a marked 
difference, reflected in the anatomical struc- 
ture, is seen between vegetative leaves and 
bracts of the inflorescence. The leaf of 
Wilkesia, which differs markedly from that of 
Argyroxiphium (Carlquist, Vygyld), appears 
much like the leaf of Dubautia laevigata in 
transection. Although the genera Dubautia 
and Wilkesia lack the intercellular deposition 
of pectic compounds which is characteristic 
of Argyroxiphium, cell walls in leaves of 
Dubautia and Wilkesia are rich in pectic com- 
pounds. Treatment of leaves of the latter with 
hydrofluoric acid prior to sectioning proved 
impracticable because the acid released such 
compounds from the wall and caused swelling 
and distortion of the leaves. The phenomenon 
described by the writer as "abaxial meristem" 
in Argyroxiphium is totally lacking in Du- 
bautia, as it is in Wilkesia. 
Leaf Venation 
Figures 7-9 show the range of venation 
types which may be seen in the genus Du- 
bautia. Dubautia lati folia (Fig. 7) is excep- 
tional for the genus in its reticulate vein pat- 
tern with polygonal areoles containing nu- 
merous freely-terminating veins. Except for the 
major veins (two of which are shown, left and 
right of center, respectively), there is no 
tendency for orientation of veins longitudi- 
nally in the leaf. D. latifolia is apparently the 
only species which has this venation pattern. 
This distinctive feature is recognized by the 
segregation of D. latifolia as a separate section 
of the genus, 'Wenoso-reticulatae' (Sherff, 
1935: 111), whereas the remainder of the 
Railliardia species are included by Sherff in 
the section ”Nervosae.'' The most typical ve- 
nation condition in Dubautia is illustrated by 
D. linearis (Fig. 9). In this species, the five 
main veins run the length of the leaf, as in 
D. latifolia. Marginal veins and those between 
the primary veins also have a distinctly longi- 
tudinal course. Areoles are more nearly rec- 
tangular, elongated with the long axis of the 
leaf. Vein endings are frequent. Dubautia 
microcephala (Fig. 8), D. plantaginea, and D. 
railliardioides show a modification of this 
pattern. In these species all of the major vena- 
tion and much of the minor venation show a 
longitudinal orientation. Areoles are very 
elongate, and vein endings are more infre- 
quent than in D. linearis. The predominant 
pattern of venation in the genus Dubautia, 
then, is like that of D. linearis, and is therefore 
a departure from typical reticulate dicoty- 
ledonous venation. One may question whether 
the reticulate venation of D. latifolia is a 
primitive condition or a "reversion.” The ad- 
vanced position of D. latifolia in characters 
