Journal of the Torrey Botanical Society 124(1), 1997, pp. 1—10

Wood anatomy of Argyroxiphium (Asteraceae): adaptive radiation and ecological correlations1 Sherwin Cariquist Santa Barbara Botanic Garden, 1212 Mission Canyon Road, Santa Barbara, CA 93105

CARLQuIsT, SHERwIN (Santa Barbara Botanic Garden, 1212 Mission Canyon Road, Santa Barbara, CA 93105). Wood anatomy of Argyroxiphium (Asteraceae): adaptive radiation and ecological correlations. J. Torrey Bot. Soc. 124: 1—10, 1997. Wood anatomy shows close correlation with ecology: A kauense, A. sandwicense (stem), and A. virescens, which occur in dry localities, show xeromorphic wood patterns. The most mesomorphic woods are those of the bog species A. grayanum and root wood of A. sandwicense. The wood of A. caliginis is xero morphic, despite the bog habitat of the species, a fact explainable if A. caliginis is a recent entrant into the bog habitat. Libriform wall thickness appears correlated with habit. Quantitative features of stem woods of Argyro xiphium are comparable to woods ranging from desert to moist montane forest areas in California. The similari ties to woods from each Californian habitat are correlative to the relative moisture availability of the respective Hawaiian habitats of the Argyroxiphium species. Key words: adaptive radiation, Argyroxiphium, ecological wood anatomy, greenswords, Hawaiian flora, silverswords.

The 28 species of the silversword alliance 1990) or leaf anatomy (Carlquist 1957), the spe (Wagner et al. 1990) comprise a monophyletic cies of Argyroxiphium are amply distinct from group that represents, in diversity of habit, ecol each other. ogy, morphology and various adaptations, the The range of habitats occupied by the species most remarkable example of plant adaptive ra is amazingly diverse: open bogs of Pu’u Kukui, diation to be found on an archipelago of oceanic W. Maui (A. caliginis); bog margins of East and islands (Carlquist 1965, 1970, 1974; Can 1985; West Maui (A. grayanurn); dry cloudy slopes of Robichaux et a!. 1990; Baldwin and Robichaux East Maui (A. virescens); dry alpine cinders and 1995). Argyroxiphium consists of five species, slopes of E. Maui and Hawai’i (A. sandwicense), Wilkesia of two, and 21 species of Dubautia are and Metrosideros forest of the rift zone of Mauna recognized (Carr, 1985; Wagner et al. 1990). Al Kea (A. kauense). Of the five species, two, A. though Argyroxiphium represents only a small kauense and A. virescens, are seriously endan portion of the silversword alliance, its five spe gered; demonstrating that either is extinct as of cies represent an amazing diversity of habitats. this date would be difficult, although either Despite marked differences among the species might be. of Argyroxiphium with respect to ecological pref The contrast between the diversity of morphol erence, all analyses, whether of chloroplast DNA ogy and physiology of the species as against the (Baldwin et al. 1990), or DNA iTS sequences genetic closeness of the species invites a study of (Baldwin and Robichaux, 1995), or enzyme elec as many features as possible. The inherent inter trophoresis (Witter, 1990), result in cladograms est of this situation is to determine in what fea that show no resolution among the species. This tures adaptive radiation can occur within a genus genetic evidence suggests that speciation within that shows relatively little genetic diversification. Argyroxiphiurn has been quite recent. The two Some data on the physiology of A. sandwicense species groups, the greenswords [A. grayanum are available (Robichaux et al. 1990), but com (Hillebr.) Degener and A. virescens Hillebrand] parative physiological data are difficult to obtain. and the silverswords [A. caliginis Forbes, A. Data on leaf anatomy have been presented (Carl kauense (Rock & M. Neal) Degener & I. Dege quist 1957). Only incomplete data on the wood ner, and A. sandwicense DCI do not reveal reso have thus far been offered (Carlquist 1958, 1994), lution into two groups with these techniques. and the present study is therefore an attempt to There is, however, no question that in terms of develop synoptic wood data for the species ofAr macromorphology (Carr 1985; Wagner et al. gyroxiphium so that the diversification in this fea ture can be portrayed as accurately as possible.

Address for correspondence: 4539 Via Huerto, Santa Barbara, CA 93110. Materials and Methods. Wood samples Received for publication July 6, 1996 and in revised (listed in Table 1) were preserved in dried form form October 4, 1996. except for the stems of A. caliginis, which were

1 2 JOURNAL OF THE TORREY BOTANICAL SOCIETY [VoL. 124

Table 1. Wood anatomical features of A;yroxiphium. Key to columns: 1 (VG), mean number of vessels per group; 2 (VD). mean lumen diameter of vessels, tim; 3 (VM), mean number of vessels per mm2; 4 (VL), mean vessel element length, tim; 5 (VW), mean vessel wall thickness, tim; 6 (FL), libriform fiber length. tIm; 7 (FW), mean wall thickness of libriform fibers, tIm; 8 (MR), mean multiseriate ray height, tinI; 9 (MW), mean multiseriate ray width, cells; 10 (FV). “F/V” Ratio (mean libriform fiber length divided by mean vessel element length); 11 (ME) “Mesomorphy Ratio” (mean vessel diameter times mean vessel element length divided by mean number of vessels per mm2. Further explanation in text; for collections, see Materials and Methods.

1 2 3 4 5 6 7 8 9 0 II Species VG VD VM VL VW FL FW MR MW FV ME A. caliginis stem 3.42 20 115 139 2.5 271 1.8 675 9.2 1.95 24 A. grayanum stem base 1.76 30 42 237 2.5 430 2.0 704 5.7 1.81 165 A. kauense stem base 5.27 15 191 191 1.2 351 2.9 589 5.8 1.84 8 A. sandwicense stem base 5.15 23 124 195 1.4 445 2.7 699 3.6 2.28 36 A. sandwjcense wider root 1.28 44 64 302 2.2 566 2.7 643 2.8 1.87 208 A. virescens stem 4.30 30 356 264 2.3 420 4.2 7 7 1.60 22 Collections averaged 3.53 32 147 221 2.0 414 2.3 662 5.4 1.89 77

preserved in aqueous 50% alcohol. The use of rable with stetTi wood of other species, but has liquid-preserved material of that species proved been included in the interests of surveying all valuable because that species has thin walled ray species. Vasicentric tracheid presence is deter cells more abundantly than do the other species. mined on the basis of macerations; sections are Paraffin sections of stems of A. caliginis that had an unreliable source for identification of vasicen been softened with hydrofluoric acid were there tric tracheids because small perforations can be fore appropriate; these sections were stained missing from a particular element by seclioiiing. with a safranin-fast green combination. A simi Ecological observations are my own; no weather lar technique (Carlquist 1982) was employed for data are available from the sites where Argyro material of A. virescens, because only limited xiphium occurs. quantities of secondary xylem were present on The collections studied are as follows: Argy that specimen. I was unable to locate any her roxiphiurn caliginis, Carlquist 550 (RSA), sum barium specimens of that species in which the mit bog of Pu’u Kukui, Maui; A .grayanum, Carl root-stem transition, which likely would have quist 2140 (RSA), margins of summit bogs, more secondary xylem, were available; the por Pu’u Kukui, W. Maui; A. kauense, Carlquist tion studied came from a region of the stem be 2110 (RSA), Kahuku Ranch, Kau District, low the leaf rosette. For A. grayaltum, A. Hawai’i; A. sandwicense, Cculquist 544 (RSA), kauense, and A. sandwicense, stems and roots Haleakala Caldera, Maui; A. vire,ccens, Degener with maximal secondary xylem accumulation 7489 (F). The material of A. ‘irescens was pro were available; these were cut on a sliding mi vided through the kindness of Dr. William crotome and stained with safranin. Macerations Burger. of all species were prepared with Jeffrey’s fluid and stained with safranin. Results. The wood plan of Argyroxiphiurn is Terms follow the IAWA Committee on No given below. Orgariographic and systematic menclature (1964). The term vasicentric tracheid variations on this basic plan are cited within is vaguely defined in that source, and a more de this description. Quantitative data are given in tailed usage (Carlquist 1988) is followed here. Table 1. Vessel diameter is measured as lumen diameter. Growth rings are absent (Fig. 1, 3, 5, 9, 13). However, most vessels are oval or even mark Vessels are more commonly grouped than soli edly flattened as seen in transection in the ge tary; the mean number of vessels per group for nus, and an attempt has been made to obtain an the genus (3.53) is indicative of this, although average diameter for vessels not close to circu solitary vessels are more common than grouped lar in transectional outline. Averages for quanti vessels in Ihe roots of A. sandwicense (Fig. 3). tative features are based on 25 measurements, Narrow vessels adjacent to larger vessels cannot except for wall thickness and pit diameter, in be identified readily in transections, because which several measures judged to be representa their diameter resembles that of libriform fibers tives are the basis for the figure presented. The (Fig. 1), but their presence can be confirmed in wood available for A. virescens, because it is not transections by observation of bordered pits in from the stem base, may not be totally compa the walls of probable narrow vessels. Differen 1997] CARLQUIST: WOOD ANATOMY OF ARGYROXIPHIIJM 3 tiation between vessels and libriform fibers in face view but in sectional view on radial transection is easiest to establish in A. kauense sections. (Fig. 12), in which libriform fibers are apprecia Storying is vaguely present in some libriform bly thicker walled than vessels. Vasicentric axial fibers and vessels of all of the species (Fig. 6; parenchyma cells are like narrow vessels in both Fig. 7, right half of photograph). No storying is diameter and wall thickness, but axial paren visible in rays. chyma is not abundant compared to the number No secretory canals are present in rays, but of narrow vessels adjacent to larger vessels. Ra large secretory canals are present in cortex. In dial sections are useful for identification of nar A. c-aliginis, sclereids are present at the periph i-ow vessels (Fig. II: all cells between the rela ery of the pith (Fig. 9, bottom). Among pith cells tively wide vessels, near left and right edges, re in this species are carbonized oleoresin depos spectively, are narrow vessels). Vessel grouping its. In the stem studied for A. virescens, which occurs in pore multiples or radial multiples (Fig. is apparently intermediate in characteristics be 1. 3, 5, 10, 12, 13). Vessels have simple perfo tween wood of lower sterns and that of inflores ration plates (one perforation plate traversed by cences, sclerenchyrna like that of the outer pith a single bar was observed in A. ealiginis). Lat in A. caligims surrounds vascular bundles, in eral walls bear pits oval in face view, about 5 which amount of secondary growth is probably p.m in vertical height, with elliptical apertures limited by the encasing sclerenchyma. No crys (Fig. 4). tals or starch grains were observed in wood cells. Imperforate tracheary elements are all libri form fibers, except that a few vasicentric tra Ecological and Habital Conclusions. Be cheids are present in groups of vei-y narrow ves cause the ecological preferences and the habits sels in A. kanense and A .sandwicense (stem of the species are rather distinctive, differences only). Libriform libers have scattered or grouped in wood anatomy may he considered systematic minute pits with an aperture length or diameter features to the extent that distinctions among the of about I p.m. Libriform fiber wall thickness species are integral to the phylesis into diverse varies (Table 1): the range is shown by compar habits and habitats. The prime indicators of di ing Fig. 10 and 12. Libriform fiber wall thick versity in wood anatomy with respect to ecol ness is greater closer to the pith in A. caliginis ogy are quantitative features of vessels. The lea (Fig. 9, lower half of photograph), whereas Ii tures most commonly cited in this respect are briform fiber wall thickness decreases during vessel diameter, vessel density, and vessel ele stem growth (Fig. 9. top half of photograph). In ment length (Carlquist 1966, 1975; Baas et al. the stems of A. virescens studied, libriform fi 1983). Degree of vessel grouping is indicative of bers are present only in the last-formed second xerornorphy also; this has been demonstrated in ary xylem. Very likely, this fiber distribution pat Asteraceae as a whole (Carlquist 1966), in which tern system is related to the fact that the stems the mean number of vessels per group (3.62) ix available are transitional to the inflorescence virtually the same as that for the species of Ar rather than from the base of the plant. gyroxiphium averaged (3.53). Asteraceae have Axial parenchyma uniformly consists of libriform fibers; vessel grouping is indicative of strands of two cells. Walls are lignified. xeromorphy in groups of dicotyledons with li Rays are multiseriate exclusively or nearly so. briform fibers or fiber-tracheids, in contrast to Erect cells predominate, but some procumbent those with tracheids (Carlquist 1984). Vessel di cells are present in the central portions of wider ameter, vessel density, and vessel length can he rays (Fig. 2, 6, 7, 8, 14). The rays thus colTe combined into an arbitrary ratio, termed the Me spond to Paedomorphic Type 11 (Carlquist 1988). somorphy Ratio (Table 1). This ratio is, in my Ray cell walls are lignified except for rays of A. opinion, an accurate indicator of the degree to caliginis (Fig. 9) and A. grayanum; in the latter, which wood of Argyioxiphium is adapted to Xe most ray cells are thin walled and nonlignified. romorphic or mesornorphic conditions. The low The relatively wide rays in A. santhi’icen,ce and est values for this ratio are A. kauense (8). the k kanense (Table I) may have a few cells with specimen of which came from relatively dry thin nonlignified walls. Ray cell walls when hg Metrosideros forest, arid A. sandu’icense (Meso— nified have a wall thickness ranging from 1 .0 to morphy Ratio for stems: 36). The habitat of A. 1.5 p.m. These lignified walls bear some bor sandsi’icense in Haleakala Caldera, Maui, is no dered pits, especially on the tangentially oriented tably dry, hut the prominently succulent nature walls. These borders can be seen readily not in of stems and leaves in that species may subordi 4 JOURNAL OF THE TORREY BOTANICAL SOCIETY VOL. 124

I

Figs. 1—4. Wood sections of Argyroxiphium sandwicense. Figs. 1—2. Wood from stem base. Fig. 1. Transec tion; no growth rings are present. Fig. 2. Tangential section; rays are exclusively multiseriate. Figs. 3—5; Wood from large root. Fig. 3. Vessels are relatively large in diameter compared to those of the stem. Fig. 4. Portion of radial section, showing simple perforation plates on vessels (below), circular bordered pits on lateral walls of vessels (above). Figs. 1—3, scale above Fig. I (divisions = 10 urn). Fig. 4, scale above Fig. 4 (divisions = 10 1997] CARLQUIST: WOOD ANATOMY OF ARGYROXIPHIUM 5

Figs. 5—8. Wood sections of Argyroxiphiurn kauense. Fig. 5. Transection; vessels are in radial multiples. Fig. 6. Tangential section; rays are wide, multiseriate. Fig. 7. Tangential section; libriform fibers at right are incon spicuously storied. Fig. 8. Radial section; both procumbent and upright cells are visible. Fig. 5, 6, scale above Fig. 1. Fig. 7, scale above Fig. 7 (divisions = 10 ii.m). Fig. 8, scale above Fig. 4.

7. Fig. above scale 10—12. Fig. 1. Fig. above 9, scale Fig. vessels.

to larger

adjacent are vessels narrow numerous Transection; A. kauense. 12. Fig. narrow. are many which of

elements, vessel

numerous shows photograph right, and left lower fibers libriforni for except section; 11. Radial

Fig.

fibers. of

nature thin—walled illustrating Outer wood, from Transection 10. Fig. wide. nolably rays below;

(dark)

sciereids pith Transection; 9. Fig. A. ca/igim,s. 9—Il Figs. Argw-oriphiwn. of sections Wood 9—12. Figs.

124 [Vo’.. SOCIETY BOTANICAL TORREY THE OF JOURNAL 6 1997] CARLQUIST: WOOD ANATOMY OF ARGYROXIPHIUM 7

Fig. 13, 14. Wood sections of Argyroxiphium grayanum. Fig. 13. Transection; vessel density is low. Fig. 14. Tangential section; rays are abundant, wide, multiseriate. Figs. 13, 14, scale above Fig. 1. nate the role of wood in achieving xeromorphy. versus non-bog plants of Metrosideros in The root of A. sandwicense has notably more Hawai’i. The fact that differentiation with re mesomorphic vessel features than does the stem spect to degree of wood xeromorphy differenti of that species. This is in accord with a trend no ates the species despite the lack of resolution of ticed quite frequently, as Patel’s (1965) summary the cladograms for the genus based on molecu shows. The Mesomorphy Ratio value of the bog lar data is interesting, because it shows how sen margin species A. grayanun is the greatest for sitive wood anatomy is as an indicator of eco stems in the genus (165). However, A. caliginis, logical adaptation. The wood of A. grayanum is which occurs in open portions of the same bogs, much more mesomorphic than that of A. caligi has a very low Mesomorphy Ratio value (24), nis, a fact which I interpret as indicating A. which I find best explained by the hypothesis grayanum adapted to the bog habitat at an ear that A. caligtnis represents a xeromorphic ances lier time than did A. caliginis. Also, A. graya try and has only recently arrived in the West num lacks the dense covering of silvery hairs, Maui bogs. This interpretation is compatible present outside A. caliginis only in species of Ar with data from leaf anatomy (Carlquist 1957). gyroxiphium from dry areas. Both species, how The number of vessels per group proves to be a ever, retain the distinctive pectic channels in very sensitive indicator of habitat in the genus. leaves, a feature that is adaptive in xeric tar- This feature (Table I) shows that A. caliginis weeds (Carlquist 1957, 1959; Morse 1990; Ro does have wood more mesomorphic than that of bichaux and Morse 1990), but probably is not of A .sandwicense and A. kauense, suggesting the negative selective value in the bog habitat and beginning of adaptation to the bog habitat. While might be of positive value even in a bog on a dwarfing of plants in bog habitats can be found day when exceptional leaf heating occurs. Al in dicotyledons at large, the leaf dimensions and though one might expect some mesomorphic plant size of A. caliginis are not notably dwarfed, features as it evolves from a dry to a wet area, whereas the bog effect usually results in appre some features may change little. For example, ciable reduction of size of all portions of a plant scalariform perforation plates are retained as a as compared to non-bog populations (e.g., bog plesiomorphy in phylads that have probably ex 8 JOURNAL OF THE TORREY BOTANICAL SOCIETY [VoL. 124 perienced uninterrupted occupancy of wet areas sessile rosettes of A. sandwicense. The wood (Carlquist 1975). Scalariform perforation plants sample available for A. virescens, apparently in have yielded to simple perforation plates as a termediate between basal stem and capitules phylad adapts progressively to areas with more cence, has very thick walled libriform fibers, and seasonal moisture availability. Should such a these fibers occur only in the last-formed por phylad return to a mesic habitat secondarily, re tion of the secondary xylem, which is finite in instatement of scalariform perforation plates amount. These secondary xylem features seem does not occur, because there is no positive Se related to the nature of this sample of A. vire lective value for these plates under those condi scens, in which the late addition of libriform fi tions (Carlquist 1975). The fact that xylem of the bers would aid in support of a capitulescence that species of Argyroxiphium has not changed more increases markedly in weight during flowering than it has as some species have entered bog situ and fruiting. ations may be explained in part by recentness of The notably wide rays of A. caliginis seem re the shift to the bog habitat. However, another lated to its habit, which has aspects of succulence factor is that features we associate with wood in degree of parenchyma presence. The moder mesomorphy (wide vessels, fewer per unit ately wide rays of the A. kauense and A. graya transection) are characteristic of canopy trees num samples may relate to the relatively great that transpire large quantities of moisture from diameter of the stems studied; an attempt was broad leaf surfaces. All of the species of Argy made to obtain wood cylinders of maximal thick roxiphium have relatively narrow leaves, and ness. Rays tend to widen as stems increase in di transpiration of water from the leaves of the bog ameter (Carlquist 1988). Wood cylinders of A. species is likely restricted by the abundance of sandwicensis do not become so thick, and that cloud cover in those habitats. may account for the more limited ray width of Both A. caliginis and A. grayanum have thin- A. sandwicense. walled nonlignified ray cells more commonly In sum, the wood of Argyroxiphium is charac than do the other species. The ecological signifi teristic of a group of shrubby or rosette-shrub cance of this is not obvious, but might be an ac Asteraceae from a dry area (comparative data commodation to shrinkage and expansion of the from Cariquist 1966). The average vessel ele stems. ment length for the genus (221 ii.m) is similar to Vasicentric tracheids are an adaptation to dry that for woods of composites from dry areas (198 conditions in plants with evergreen leaves, urn). Vessel elements in Argyroxiphium may be probably because under water stress conditions, a little longer than those of xeric Asteraceae be vasicentric tracheids would embolize less cause the smaller thickness of woody cylinders readily than the vessels they accompany. The in Argyroxiphium may involve paedomorphosis, vasicentric tracheids could thereby provide a one feature of which is vessel elements longer continuous water supply to leaves (Cariquist than expected for a given ecological site (Carl 1985). The two silversword species from drier quist 1962). The mean vessel diameter of Argy conditions, A. sandwicense (Carlquist 1994) roxiphium (32 urn) is very close to what the lu and A. kauense, have vascentric tracheids in men diameter would be for vessels of xeric As moderate quantities. Occasional vasicentric tra teraceae, projecting from the data of Carlquist cheids were observed in a maceration made (1966), in which external diameter rather than lu from A. virescens wood. Vasicentric tracheids men diameter was measured. If compared to were not observed in the bog species A. catigi wood features of Asteraceae as a whole, the nis and A. grayanum, a fact that indicates that wood of Argyivxiphium corresponds to woods this cell type, minor though its significance from “dry” or “desert” species in the family sur might be, may have disappeared during phy vey (Carlquist 1966). lesis into wetter conditions. The quantitative picture of wood of Argyro The libriform fibers of A. kauense are rela xiphium as xeromorphic has a counterpart in the tively thick walled compared with other species xerornorphic leaf features of the genus (Carlquist of Argyroxiphium and do not decrease in wall 1957). On the basis of anatomical evidence, then, thickness with increase in stem diameter as do the origin of Argyroxiphium seems to have been those of A. caliginis. This feature of A. kauense in now-vanished alpine regions of Kaua’i, a pos may relate to the stalked rosettes of A. kauense, sibility envisioned by Baldwin and Robichaux which would therefore be expected to have (1995). The lack of an alpine zone on the two greater mechanical strength than wood of the major islands preceding Kaua’i—Nihoa and 1997] CARLQUIST: WOOD ANATOMY OF ARGYROXIPHIUM 9

Necker—when those islands were at maximum Literature Cited elevation would render those two islands less likely as sites for origin of Argyroxiphium if the BAAs, P, E. WERKOR, AND A. FAHN. 1983. Some eco logical trends in vessel characters. IAWA Bull., genus derives from ancestors like A. sandwi 4: 141-159. cense (Carson and Clague 1995; Carlquist 1995). BALDwIN, B., D. W. KyHos, AND J. DvoRAK. 1990. Origin of Argyroxiphium on a post-Kaua’i island Chloroplast DNA evolution and adaptive radiation (O’ahu or Maui-nui) does not accord with cia in the Hawaiian silversword alliance (Madiinae, As teraceae). Ann. Missouri Bot. Garden distic evidence showing the primary radiation of 77: 96—109. AND R. H. Roalci-tAux. 1995. Historical bio the silverword complex on Kaua’i (Baldwin and geography and ecology of the Hawaiian silver Robichaux 1995), although part of the diversifi sword alliance (Asteraceae): new molecular phylo cation within Argyroxiphium has likely occurred genetic perspectives, p. 259—287, In W. L. Wagner on post-Kaua’i islands. and V. Funk (eds.), Hawaiian biogeography, evolu tion on a hot spot archipelago. Smithsonian Insti All cladistic evidence shows that the diversi tution Press, Washington, D.C. fication of Argyroxiphium is recent (all clad CARLQuIsT, 5. 1957. Leaf anatomy and ontogeny in ograms based on molecular data show the spe Argyroxiphium and Wilkesia (Compositae). Amer. J. cies unresolved). Data from wood and leaf Bot. 44: 696—705. 1958. Wood anatomy of Heliantheae anatomy are consistent with a picture of origin (Corn positae). Trop. Woods 108: 1—30. of Argyroxiphium in some kind of alpine habi 1959. Studies on Madiinae: anatomy, cytol tat, with relatively rapid entry into other high- ogy, and evolutionary relationships. Aliso 4: 171— elevation habitats, some markedly mesic. If one 236. were to suppose, instead that the history of Ar 1962. A theory of paedomorphosis in dicoty ledonous woods. Phytomorphology 12: 30—45. gyroxiphium proceeded from mesic to xeric, the 1965. Island life. Natural History Press, New pervasive xeromorphic adaptations of wood and York. leaf in the genus and the extremely xeric habi 1966. Wood anatomy of Compositae: a sum tats occupied by Argyroxiphium (combined with mary, with comments on factors controlling wood evolution. Aliso 6: 25—44. absence of the genus in intermediate habitats) 1970. Hawaii a natural history. Natural His would be difficult to explain. If compared to Me tory Press, New York. somorphy Ratio values (as well as the vessel di 1974. Island biology. Columbia University mensions on which they are based) for Califor Press, New York. nian woody plant species (Carlquist and Hoek 1975. Ecological strategies of xylem evolu tion. University of California Press, Berkeley and man 1985), the Mesomorphy values are very Los Angeles. similar: in California, these range from 21 1982. The use of ethylene diamine in soften (desert) to 106 (moist forest habitats), which is ing hard plant structures for paraffin sectioning. similar to the range from A. kauense (8) to A. Stain Technol. 57: 311—317. 1984. Vessel grouping in dicotyledon grayanum (165). woods: significance and relationship to imperforate trache The data in the present study cannot be ary elements. Aliso 10: 505—525. appropriately polarized for presentation in stan 1985. Vasicentric tracheids as a drought sur dard cladistic fashion. One cannot with assur vival mechanism in the flora of southern Califor ance separate phenotypic modifications from nia and similar regions; review of vasicentric tra cheids. Aliso 11: 37—68. genetically fixed features under genetic control. 1988. Comparative wood anatomy. Berlin Moreover, such a xeromorphic feature as nar and Heidelberg, Springer Verlag. rowing of vessels would show up in a clad 1994. Anatomy of tropical alpine plants, p. ogram as a homoplasy, and might only provide 111—128. In P. W. Rundel, A. P. Smith, and F. C. Meinzer (eds.), Tropical alpine environments. noise level in cladogram construction. Some Cam bridge University Press, Cambridge. attempts to use xeromorphic features in cladis 1995. Introduction, pp. 1—13 In W. L. Wag tic analysis have resulted in defining taxonomic ner and V. A. Funk (eds.), Hawaiian biogeography, categories in terms of degree of xeromorphy evolution on a hot spot archipelago. Smithsonian instead of degree of relationship. Features of Institution Press, New York. AND D. A. I-I0EKMAN. 1995. Ecological wood phyletic significance can be extracted from anatomy of the woody southern Californian flora. wood data for large groups in which the “noise IAWA Bull., n. s., 6: 3 19—347. level” of numerous fluctuations in ecological CARR, G. D. 1985. Monograph of the Hawaiian Ma shift do not play a significant role. However, no diinae (Asteraceae): Argyroxiphium, Dubautia, and Wilkesia. Allertonia 4: satisfactory resolution to the problem has been 1—123. CARsON, H. L., AND D. A. CLAGuE. 1995. Geology obtained in recently-evolved groups such as the and biogeography of the Hawaiian Islands, p. 14— species of Argyroxiphium. 29. In W. L. Wagner and V. A. Funk (eds.), Hawai 10 JOURNAL OF THE TORREY BOTANICAL SOCIETY [VOL. (24

ian biogeography, evolution on a hot spot archi Hawaiian bog species, Aigyioxiphi,im gravanum pelago. Smithsonian Institution Press, Washington, (Compositae—Madiinae). Amer. J. Bot. 77: 134— D.C. 138. 1AWA CoMMITTeE ON NOMENcLATURE. 1964. Multi G. D. CARR, M. LIEBMAN, AND R. C. PEARcy. lingual glossary of terms used in wood anatomy, 1990. Adaptive radiation of the Hawaiian silver- Konkordia, Winterthur. sword alliance (CompositaeMadiinae). Ann. MoRsE, S. R. 1990. Water balance in Hernizonia in Missouri Bot. Garden 77: 64—72. zulifolia: the role of extracellular polysaccharides. WAGNER, W. L.. D. R. HERBSI. AND S. H. S0HMER. Plant Cell Environ. 13: 39—48. 1990. Manual of the flowering plants of Hawai’i. PATEL, R. N. 1965. A comparison of the anatolny of University of Hawai’i Press and Bishop Museum the secondary xylem in roots and stems. Holzfors Press, Honolulu.

chung 19: 72—79. WIrrER. . S. 1990. Evolution in Madiinae: evidence RoBIcHAux, R., AND S. R. MoRsE. 1990. Extracellu from enzyme electrophoresis. Ann. Missouri Bol. lar polysaccharides and leaf capacitance in a Garcl. 77: 110—117.