IAWA Bulletin n.s., Vol. 6 (1),1985 23 THE ANATOMY OF THE BARK OF LlBOCEDRUS IN NEW ZEALAND by Lek-Lim Chan'" School of Forestry, University of Canterbury, Christchurch, New Zealand Summary The anatomy of the bark of Libocedrus bid­ southwards. In South Island it is also found in willii and L. plumosa, both indigenous to New lowland forests in the west. Libocedrus plumosa Zealand, is described. The phloem cell types in­ is also a tall tree and is found in lowland forest clude axial and ray parenchyma, sieve cells and from 35° to beyond 38° S in North Island and fibres. Fibres are of two types, thin-walled and between Collingwood and Westhaven (NW. Nel­ thick-walled. The ends of these fibres are most­ son) in South Island. ly blunt or abrupt. Minute crystals (crystal sand) were found in Terminology the radial walls of some axial parenchyma cells, 'Conducting phloem' refers to that part of sieve cells and fibres. Trabeculae were abun­ the phloem close to the vascular cambium where dant in the bark of L. bidwillii. sieve cells are still functioning in conduction, The walls of the phellem cells were very thin, and 'living bark' designates that part of the appearing flimsy. Phelloderm cells in L. plumo­ bark outside the vascular cambium up to and sa seem to undergo sclerification just prior to including the last-formed periderm. death, upon formation of a new periderm deep­ All other terms used for tissues of the bark er in the phloem. are in common usage (see IA WA, 1964; Society Key words: Bark anatomy, crystals, Libocedrus, of American Foresters, 1958). trabeculae. The approximate size of crystals is given as a length which refers to the greatest length (or Introduction diameter) across the crystal. Information on the anatomy of bark is rela­ tively scanty, compared to that of wood. Only Materials and Methods a few extensive studies have been made on the Three trees each of Libocedrus bidwillii and bark of gymnosperms indigenous to New Zea­ L. plumosa were selected from Inangahua West land. and Omahuta State Forests respectively. Two Craddock (1932a) made a study of the barks specimens of the bark from opposite sides of of Podocarpaceae in New Zealand but only an each tree at breast height were collected. The abstract of this work was published (Craddock, specimens were immediately fixed in 5 % glutar­ 1932b). Robinson and Grigor (1963) examined aldehyde in 0.025 M phosphate buffer and left the origin of the periderm in some New Zea­ in the fixative until sectioning. land plants including eight members of the Podo­ Observations were made using optical (LM) carpaceae family and Agathis australis. Kucera and scanning electron (SEM) microscopy. For and Butterfield (1977) investigated the resin optical microscopy, sections (c. 30 J.Lm in thick­ canals in the bark of New Zealand Phyllocladus ness) were cut without embedding or further species. However, investigations on the bark of treatment on a Reichert 'OrnE' sledge micro­ the Cupressaceae indigenous to New Zealand tome from blocks of bark not bigger than 7 x 5 have never been carried out. This present work mm on the cutting face. Sections were picked is a continuation of an earlier report (Chan et up from the microtome knife with a fine hair aI., 1982). brush wetted with 25 % alcohol and then left in Two species of Libocedrus (Cupressaceae) a petri-dish with 45 % alcohol until stained. They occur naturally in New Zealand, namely L. bid­ were double-stained with safranin and fast green. willii and L. plumosa (Allan, 1961). This small Macerations were also carried out by heating genus has only three other species, all endemic match-stick size specimens in a solution of equal to New Caledonia (Dallimore & Jackson, 1966). amounts of glacial acetic acid and 20 volume Libocedrus bidwillii is a tall tree found in mon­ hydrogen peroxide in a water-bath for about tane to subalpine forests, distributed in both 1-2 hours. The tissue was then stained with North and South Island, from 36° 50' latitude 1.5% aqueous safranin, washed and teased out. * Present address: St. Peter's College, P. O. Box 327, Kuching, Sarawak, Malaysia. Downloaded from Brill.com10/01/2021 11:02:14AM via free access 24 IAWA Bulletin n.s., Vol. 6 (1),1985 For SEM observations, the specimens were most with rather blunt or abrupt ends like pa­ prepared by hand, following the method out­ renchyma cells (Fig. 2C). Thin-walled fibres lined by Exley et al. (1974, 1977). It was neces­ have numerous slit-like pits. The walls of both sary to take the specimens through a progres­ thin- and thick-walled fibres are lignified, bire­ sive alcohol series and critical-point drying. For fringent and seem to be composed of two main examination of wall structure, soaking in 5% layers. The wall of thin-walled fibres consists of sodium hypochlorite prior to the alcohol series one very thin layer on the outside and one thin was required to remove cell deposits. Dried spe­ layer on the inside, while in thick-walled fibres cimens were coated with gold in a Polaron it consists of one thin layer on the outside and Diode Sputtering System E500 and examined one thick layer on the inside. Some minute in a Cambridge Stereos can 600. crystals « 4 J.Lffi long), mostly hexagonal pris­ matic in shape, are round in the radial walls of Descriptions fibres (in the region of the middle lamella). In all specimens studied, trabeculae were ex­ Libocedrus bidwillii Hook. f. tremely common, all traversing in the radial di­ The diameters at breast height of the trees rection from one tangential wall to the next were 65.6 cm, 13.7 em and 18.0 cm and the (Fig. 2B, D). thickness of the living bark at the same height The periderm consists of 2-3 layers of phel­ was 3.8 mm, 4.5 mm and 3.0 mm respectively. lem, one layer of phellogen and 2-3 layers of The phloem consists of sieve cells, axial and phelloderm. Phelloderm cells are oblong in TS ray parenchyma and fibres, arranged in regular and rectangular to oblong in RLS. In TLS, tangential rows (Fig. lA, B). Every row of axial those phelloderm cells cutoff by phellogen parenchyma cells always has a row of sieve cells derived from axial parenchyma cells appear on either side. These sieve cell-parenchyma­ rectangular to six-sided while those from ray sieve cell rows are separated by 1-2, rarely 3, parenchyma cells are rather isodiametric and rows of fibres (Fig. 1C). The conducting phloem smaller than the former (Fig. 3A). Phelloderm seems to be about 0.7-0.8 mm wide. cells have thin walls; some contain tannin, as Sieve cells appear rectangular in transverse do some phellogen cells. Phellem cells are rec­ section (TS), becoming narrowly rectangular in tangular in TS and RLS. In TLS, phellem cells the non-conducting phloem. Some minute crys­ are of two shapes corresponding to phelloderm tals « 4 p.ffi long), mostly hexagonal prismatic cells in TLS. Those phcllem cells derived from in shape, appear in their radial wall, bu t are some­ ray parenchyma cells often have some tannin times absent in the non-conducting phloem. contents while those from axial parenchyma Sieve areas are about 6-9 !lm in diameter, cells do not. Phellem cells are very thin-walled, mostly in the radial walls in single files. the walls appearing rather flimsy (Fig. 3B). Axial parenchyma cells are rectangular to Dead periderm and phloem are not exfoliated isodiametric in TS and rectangular in radial lon­ readily, leading to the formation of a thick rhy­ gitudinal section (RLS) and tangential longi­ tidome which consists of alternating layers of tudinal section (TLS). They are mostly filled dead periderm and phloem. Fibres and sieve with tannin. Some minute crystals « 4 J.Lffi cells remain intact but parenchyma and phello­ long), mostly hexagonal prismatic in shape, derm cells collapse markedly in the radial direc­ appear to be located in the radial wall of some tion (Fig. 3C, D). parenchyma cells but are sometimes absent in the non-conducting phloem. Libocedrus plumosa (Don) Sargent Phloem rays are uniseriate, rarely partly bi­ The diameters at breast height of the trees seriate, usually 1-7 cells high (up to 12 count­ were 33.4 cm, 41.5 cm and 39.5 cm, and the ed). The cells appear rectangular in TS and thickness of the living bark at the same height RLS, and round to elliptical (with long axes in was 3.8 mm, 4.6 mm and 3.8 mm respectively. the longitudinal direction) in TLS (Fig. 2A). The phloem comprises sieve cells, axial and Fibres are of two types, thin- and thick­ ray parenchyma and fibres, arranged in regular walled. They are mostly thin-walled with large tangential rows (Fig. 4A, B). Every row of axial empty lumina (Fig.lC, 2A). Thick-walled fibres parenchyma cells always has a row of sieve cells have very narrow lumina and are scattered in on either side. These sieve cell-parenchyma­ the phloem, rarely forming a tangential row sieve cell rows are usually separated by a row (Fig. lA, B, C). Both thin- and thick-walled of fibres (Fig. 4C). The conducting phloem is fibres appear square to rectangular (with long about \.6-2.0 mm wide. axes in the radial direction) in TS and elongated Sieve cells appear rectangular in TS with little with pointed ends in TLS (Fig. 2A). In RLS, change in the non-conducting phloem. Some some appear elongated with pointed ends, but minute crystals, mostly hexagonal prismatic in Downloaded from Brill.com10/01/2021 11:02:14AM via free access IAWA Bulletin n.s., Vol.