Abstract

Qualitative and quantitative data are presented for wood of all species of Fouquieriaceae, the samples selected so as to cover important variables with respect to organography and age. Wood contains fibertracheids (plus a few vasicentric tracheids). Diffuse axial parenchyma is mostly grouped as diffuse-in-aggregates or diffuse clusters (new term), with transitions to pervasive axial parenchyma in some species. Rays are Heterogeneous Type II. These wood features are relatively unspecialized and are consistent with placement of the family in Ericales s.1. as defined in recent DNA-based cladograms. Xeromorphic wood in nonsucculent species occurs only in Fouquieria shrevei; the lateral branches of F. columnaris also have xeromorphic wood. If the preceding two instances and proliferated parenchyma of the three succulent species (F. columnaris, F. fasciculata, and F. purpusii) are excluded from quantitative studies, wood of Fouquieriaceae is rather mesomorphic, despite the habitats occupied by the family. This paradox is explained by the very sensitive drought deciduousness. Also, the succulent species produce water-storage parenchyma by means of expansion of rays and axial parenchyma bands. Details of these two types of meristems, as well as three other types of meristems within wood (not including vascular cambium) and four bark meristems (other than phellogen) are described; five of these meristems are newly reported for the family. Wood data permit recognition of both the three succulent and eight nonsucculent species within a single genus, in agreement with Henrickson (1972), but few wood features offer species characters. Most wood features, including the abundant reaction wood, are closely related to habit, organography, and ecology.

Highlights

  • Little published work on wood of Fouquieriaceae exists (Gregory 1994), despite the inherent interest of this distinctive family, which exhibits such diverse habits in a variety of dry habitats of Mexico and the southwestern United States (Henrickson 1969a)

  • The plans of stems as seen in transections in gross aspect have been well figured by Henrickson (1969b, 1972) and need not be repeated here, Henrickson's thesis (1968) presented both quantitative and qualitative data on the secondary xylem of the family, The wood and bark sections studied here are preparations by the author that represent new techniques, including paraffin sectioning to reveal delicate cells intermixed with sclerenchyma (Carlquist 1982), sensitive counterstaining, and scanning electron microscopy (SEM)

  • The following brief descriptions are offered to summarize the surprising diversity within the family and to introduce the taxonomy of the family: Fouquleria subgenus Idria : F. columnaris (Kellogg) Kellogg ex Curran: trees to 23 m with an usually unbranched trunk tapering upwards, hearing numerous slender horizontal lateral branches

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Summary

INTRODUCTION

Little published work on wood of Fouquieriaceae exists (Gregory 1994), despite the inherent interest of this distinctive family, which exhibits such diverse habits in a variety of dry habitats of Mexico and the southwestern United States (Henrickson 1969a). & Schult.) Nash: shrubs or small trees 2-5 m tall with 1-3 succulent trunks, branches slender, upright to diagonal. Brandegee: shrubs or small trees to 5 m tall, with 1-5 tapering succulent trunks, branches slender, upright to diagonal. The habit of F. columnaris is distinguished from those of the two species of subgenus Bronnia, all three may be described as succulent trees because of the thick stems (main trunks) largely composed of parenchyma. The two species of section Ocotilla are highly distinctive in their numerous branches that diverge from near the base of the plant; F. shrevei is like a somewhat dwarfed version of F. splendens, the range within F. splendens is considerable, and three subspecies of F. splendens were recognized by Henrickson (1972). Fouquieriaceae: Wood Anatomy and Meristems better understanding of cambial variants and bark development in dicotyledons as a whole

MATERIALS AND METHODS
Ray Expansion
Formation of Se condary Parenchyma Tissue in the Stem Center
Cylindrical Meristems Around Vascular Strands
Occasional Late Divisions in Axial Parenchyma
Cortical Water Storage Tissue Meristems
Sclereid Band Maintenance Meristems
Sclereid Nest Meristems in Bark of Succulent Fouquierias
Secondary Starch Sheath Meristems in Bark
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