Anatomy of Gymnosperms Endemic to China, II. Taiwania flousiana Gaussen (Taxodiaceae)

Abstract

Abstract:

Taiwania Hayata contains two species: T.flousiana Gaussen and T. cryptomerioides

Hayata, both endemic to China.

T. flousiana was investigated with both light and scanning electron microscopes in respect

to shoot apex, external and internal surfaces of leaf cuticle, primary leaf, juvenal and mature

leaves, young stem, secondary phloem and wood of stem, etc,

It is shown that the shoot apex consists of the following five regions: (1) the apical initials;

(2) the protoderm, (3) the subapical moher cells;. (4) the peripheral meristem, and (5) the

pith mother cells. The periclinal and anticlinal division of the apical initials takes place with

approximately equal frequency.

The juvenal leaf is nearly triangular or crescent-shaped in cross section and belongs to

the leaf type II. The mature leaf is quadrangular in cross section (the leaf type I). There are

a progressive series of changes in size and shape of the leaf cross section. The stoma of the ma-

ture leaf is amphicyclic and occasionally tricyclic. The crystals in the juvenal leaf cuticle are

more abundant than those in the mature leaf cuticle. The transfusion tissue conforms to the

Cupressus type. The structure of juvenal leaf is the nearest to that in Cunninghamia unicana-

liculata D. Y. Wang et H. L. Liu, while the mature leaf is similar to that of the Cryptomeria.

Sclerenchymatous cells of the hypodermis in the young stem comprise simple layers and are

arranged discontinuously. No primary fibers are found in the primary phloem. Medullary

sheath is present between the primary xylem and the pith. There are some sclereids in the pith.

The secondary phloem of the stem consists of regularly alternate tangential layers of cells

in such a sequence: sieve cells, phloem parenchyma cells, sieve cells, phloem fibers, sieve cells.

The phloem fiber may be divided into thick-walled and thin-walled phloem fiber. The cry-

stals of calcium oxalate in the radial walls of sieve cells are abundant. Homogeneous phloem

rays are uniseriate or partly biseriate, 1-48 (2-13) cells high, and of 26-31 strips per square

mm.

Growth rings of the wood in Taiwania are distinct. The bordered pits on the radial walls

of early wood tracheids are usually uniseriate, occasionally paired and opposite pitting. Wood

parenchyma is present, and its cells contain brown resin substances. Their end walls are smooth,

lacking nodular thickenings. Wood rays are homogeneous. Cross-field pits are cupressoid. Resin

canals are absent.

Based on the anatomy of Taiwania and comparison with the other genera of Taxodiaceae,

the authors consider the establishment of Taiwaniaceae not reasonable, but rather support the

view that the genus is better placed between Cuninghamia and Arthrotaxis in Taxodiaceae.

Key words: Taiwania, Taiwania flousiana, anatomy, systematic position

Hu Yu-Shi, Ma Rui-Jun. Anatomy of Gymnosperms Endemic to China, II. Taiwania flousiana Gaussen (Taxodiaceae)[J]. .

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Anatomy of Gymnosperms Endemic to China, II. Taiwania flousiana Gaussen (Taxodiaceae)

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