WOOD ANATOMY OF OBOLINGA (MIMOSACEAE) REGIS B. MILLER

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1 Brittonia, 41(2), 1989, pp , by the New York Botanical Garden, Bronx, NY WOOD ANATOMY OF OBOLINGA (MIMOSACEAE) REGIS B. MILLER Miller, Regis B. (Center for Wood Anatomy Research, Forest Products Laboratory, One Gifford Pinchot Dr., Madison, WI ). Wood anatomy of Obolinga (Mimosaceae). Brittonia 41: Thewood anatomy of Obolinga zanonii Barneby (tribe Ingeae) is described based on three specimens representing three trees. The wood of Obolinga is very similar to that of Cojoba, a segregate of the Pithecellobiurn complex. They differ only in the color and fluorescence of water and ethanol extracts. In this issue of Brittonia, Barneby (1989) describes a new mimosoid legume genus in the tribe Ingeae which he calls Obolinga. This is a monotypic genus (O. zanonii Barneby) and the species is named after Thomas A. Zanoni who collected the type and wood specimens for this study. I was invited by Dr. Barneby to examine the wood to provide additional anatomical data that subsequently would clarify the relationships within Mimosaceae and the tribe Ingeae. Materials and Methods Three vouchered wood samples representing three trees of Obolinga zanonii were available for study-a 5-cm-diameter branch sample without heartwood from the type tree (Zanoni & García 35610, MADw ); a small diameter (10-13 cm) sample with only a trace of heartwood (Zanoni & Garcia A, MADw 44040); and a large diameter ( cm) sample with heartwood (Zanoni & García 36296, MADw 44034). The wood samples are housed at MADw and the vouchers are housed at JBSD and NY, and are cited by Barneby (1989). In the tribe Ingeae, 22 of 35 genera listed by Nielsen (1 981, Table 1, pp ) were available for study in the MADw and SJRw 2 wood collection. I cut sectioning blocks from the outer portion of the sapwood in all three samples. In the large diameter sample block, however, I also cut a block from the heartwood near the heartwood-sapwood boundary. In general I followed standard microtechnique practices and four slides were made from each block; two were stained with safranin and two remained unstained. Material for maceration was taken from near the cambial area to obtain the most recently-formed cells. Only unstained temporary mounts were made with 50:50 glycerin-alcohol. Observations and measurements follow the procedures described by Miller (198 1) with the exception of pores per square millimeter. In this particular case each pore or opening is counted as a single unit, and percent solitary pores is calculated by dividing the total number of pores (openings)into the number of solitary pores (Wheeler, 1986). In addition I determined the percentage of uni-, bi-, and triseriate rays. I counted the number of uni-, bi-, and triseriate rays per field until at least 200 rays were counted (approximately 10 fields), and then calculated the percentage based on the total number of rays. Intervascular pits were examined with the SEM (scanning electron microscope) to determine if they were vestured. Samples for examination were treated with household bleach to remove encrustations (Quirk & Miller, 1985). 1 MADw is an acronym for one of the wood collections housed at the Forest Products Laboratory, Madison, Wisconsin, USA. 2 SJRw is an acronym for the Samuel James Record Memorial wood collection housed at the Forest Products Laboratory, Madison, Wisconsin, USA.

2 1989] MILLER: OBOLINGA WOOD ANATOMY 179 Wood Description All features listed in the Standard List of Characters Suitable for Computerized Hardwood Identification (IAWA Committee, 1981) were examined, but only the major or positive features of O. zanonii are reported. Features from the standard list not mentioned specifically in the description are absent or negative. General Features Sapwood white to pale cream or tan, distinct from the reddish-brown heartwood, which sometimes appears streaked due to tension wood. Texture medium to slightly coarse, grain slightly interlocked. Growth rings absent. Specific gravity (ovendry weight/green volume) Under longwave ultraviolet lamp heartwood fluoresces pale yellow; water and ethanol extract colorless and not fluorescent. Splinter bums to gray or white ash, chrome azurol-s test negative, and froth test positive. Deposits in vessel not observed. Microscopic Features Vessels diffuse, solitary (40-80%) and in short radial multiples of 2 or 3; 5-10 (12) per mm 2, mostly round; diameters ranging from µm (av. 118 µm) (Fig. 1); vessel element length µm (av. 305 µm). Perforations simple, end walls nearly transverse; tyloses absent. Intervascular pitting alternate, 2-4 µm; vessel-ray pits same size and shape as intervascular pits; vestured (Fig. 3). Fibers nonseptate with small pits, occasionally gelatinous; walls thin to thick; length µm (av µm). Rays homocellular, not storied, 8-17 per mm, uni- to biseriate, occasionally triseriate; 82% uni-, 17% bi-, and 1% triseriate in the branch sample; 53% uni-, 46% bi-, and 1% triseriate in the mid-sized sample; and 47% uni-, 50% bi-, and 3% triseriate in the large sample (Fig. 4). Total ray height µm (av. 230 µm); average of the 10 largest 255 µm. Ray cell height 12-14µm. Paratracheal parenchyma vasicentric to aliform, sometimes forming narrow confluent bands; apotracheal parenchyma occasionally in narrow (1 or 2 cells wide), marginal, or irregular zonate bands and rarely to occasionally diffuse (Fig. 1); strands mostly fusiform or 2-celled, occasionally 4-celled. In MADw idioblastic or inflated fusiform axial parenchyma cells common (Figs. 1, 5), without contents, generally in a diffuse arrangement; rare to occasional in the other two specimens. Prismatic crystals present in axial parenchyma in long crystalliferous chains, generally 8 to 16 crystals per chain. Discussion and Conclusion At first glance, even with a 14 hand lens, I easily recognized the wood of Obolinga as that of a legume. More detailed observations with a microscope identified it as that of a mimosoid legume in or near the Pithecellubium Mart. complex (tribe Ingeae), and in particular similar to the wood of Cojoba Britton & Rose. Cassens and Miller (1 98 1) studied the wood anatomy of the New World species of Pithecellubium (sensu lato), which included species now assigned to Cojoba. We concluded that the Pithecellubium complex can be separated into four distinct anatomical groups based on the presence or absence of septate fibers and confluent parenchyma. Group 1, which contains Cojoba, has both nonseptate fibers and confluent parenchyma. Other genera or wood-types in this group include Samanea Merr., Abarema Pitt., Pseudosamanea Harms, Chloroleucum Britton & Rose ex Record, and Ebenopsis Britton & Rose. Features that distinguish Cojoba from these genera include moderately short vessel elements (av. 324 µm), medium-

180 BRITTONIA [VOL. 41 FIGS. 1-4. 1 & 2. Transverse sections of wood showing medium-sized pores and aliform to confluent parenchyma. Arrows indicate idioblastic axial parenchyma cells, 53. 1. Obolinga zanonii (Zanoni & García 36296, MADw 44034).

3 180 BRITTONIA [VOL. 41 FIGS & 2. Transverse sections of wood showing medium-sized pores and aliform to confluent parenchyma. Arrows indicate idioblastic axial parenchyma cells, Obolinga zanonii (Zanoni & García 36296, MADw 44034). 2. Cojoba arborea (Mathews & Crosby 67, SJRw 9220). 3. SEM photomicrograph of 0. zanonii (Zanoni & García 35610, MADw 42807) showing vestured pits 3-5 µm in diameter, 10, Tangential section of O. zanonii (Zanoni & Garcia A, MADw 44040) showing ray type, width, height, and general arrangement, 130.

1989] MILLER: OBOLINGA WOOD ANATOMY 181 FIGS. 5 & 6. Idioblastic or inflated axial parenchyma cells indicated by arrows, 130. 5. Radial section of Obolinga zanonii (Zanoni & García 36296-A, MADw 44040).

4 1989] MILLER: OBOLINGA WOOD ANATOMY 181 FIGS. 5 & 6. Idioblastic or inflated axial parenchyma cells indicated by arrows, Radial section of Obolinga zanonii (Zanoni & García A, MADw 44040). 6. Tangential section of Cojoba arborea (Fors 953, MADw 13967). sized pores (av. 171 µm), red-brown heartwood, and very small to minute (3-5 µm diam) intervascular pits. In fact, species of Cojoba are the only ones in Pithecellobium (sensu lato) that have vessel pitting 3 to 5 µm in diameter, and in the tribe Ingeae only a few species of Calliandra Benth. have this type of pitting. Comparing the microscopic features of Obolinga and Cojoba, I found that the pore diameter, frequency, and arrangement (Fig. 2), and fiber and vessel element length and sculpturing were nearly identical. The ray structure and parenchyma were also so similar that no differences were noted. Cassens and Miller (198 1) did not report the presence of idioblastic or inflated axial parenchyma cells in any of the Pithecellobium complex, but upon re-examination of some specimens of Cojoba, these cell types were found (Fig. 6). They were generally not as large and frequent as in Obolinga (Figs. 1, 5), but nonetheless they are the same cell type. In addition, I re-examined every other genus in the Pithecellobium complex and only found these unique cells rarely or occasionally in a few specimens of Chloroleucum, Macrosamanea Britton & Killip, Samanea, and Zygia P. Browne. Since this cell type occurs sporadically, it cannot be a useful diagnostic feature. It is, perhaps, a response to an environmental influence, but without more material this aspect cannot be clarified. However, this cell type appears to occur in specimens from smaller diameter trees and sometimes is associatedwith tension wood. In any case, idioblastic axial parenchyma cells were larger and more common in Obolinga and Cojoba than in any other species in the Pithecellobium complex. The physical properties and macroscopic wood anatomy of Obolinga and Cojoba are indistinguishable. However, when I compared the results of chemical tests from the standard list (IAWA Committee, 1981), I found what appears to be a slight difference between the two genera. The heartwood fluorescence and

182 BRITTONIA [VOL. 41 froth tests were positive and the chrome azurol-s and burning splinter tests were negative in both genera. The only difference I noted was in the water and ethanol extracts.

5 182 BRITTONIA [VOL. 41 froth tests were positive and the chrome azurol-s and burning splinter tests were negative in both genera. The only difference I noted was in the water and ethanol extracts. In Obolinga (only one sample with an appreciableamount of heartwood) both the water and ethanol extract were essentially colorless and not fluorescent. I tested 16 specimens of Cojoba and found the following: water extract color light brown to brown, occasionally with a tinge of red, fluorescence generally positive with a blue or greenish-blue color; ethanol extract colorless to brown, occasionally with a slight tinge of red, fluorescence weakly positive to positive with a blue to definite green color. In all 16 specimens of Cojoba the water and ethanol fluorescence was more intense than that of Obolinga, and in most specimens some color was noted in the extract. However, even a few samples of Cojoba were colorless and weakly fluorescent. These differences are fairly reliable wood identification characters, but there is little information to substantiate or suggest that they indicate relative relationships or phylogenetic trends except for the intuitive similarity of conditions. Since I had only one sample of Obolinga that contained heartwood, I cannot be certain that this specimen was typical and representative. In conclusion I found that the woods of Obolinga and Cojoba are so similar they cannot be separated with any degree of certainty. This does not negate the formation of a new genus, but it does indicate a very close relationship. Acknowledgments I wish to thank Thomas A. Zanoni for collecting wood samples without which this study could not have been initiated. Thanks are also due Thomas Kuster for the SEM photomicrographs and to Rupert Barneby and T. A. Zanoni for reviewing the manuscript. Literature Cited BOOKS RECEIVED Handbook of Indian Foods and Fibers of Arid America. By Walter Ebeling. University of California Press, 2120 Berkeley Way, Berkeley, CA ISBN pp. $75 (cloth). A Functional Biology of Crop Plants. By Vincent P. Gutschick. Timber Press, Inc., 9999 S.W. Wilshire, Portland, OR ISBN pp. $39.95 (cloth). TerrestrialPlant Ecology. Second Edition. By Michael G. Barbour, Jack H. Burk, and Wanna D. Pitts. Benjamin/Cummings Publishing Co., 2727 Sand Hill Road, Menlo Park, CA ISBN pp. $39.95 (cloth). Stomatal Function. Edited by Eduardo Zeiger, G. D. Farquhar, and I. R. Cowan. Stanford University Press, Stanford, CA ISBN pp. $65 (cloth).

Angiosperms: Dicotyledons

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