Pith helmets adrift and rootwood from the Swamps

Pieter Baas, Bertie-Joan van Heuven & Nancy Vander Velde

Contents

• Mysterious driftwood from the Marshall Islands

• Identification of mystery rootwood• A royal wood sample from Tervuren• Two pith helmet samples from Kew• Peculiar wood structures in swamps

and inundation forests• A mysterious trunk of “Balsa” in Leiden

Nancy Vandervelde sitting on driftwood

Traditional use of Light Driftwood

• Cheap Cork substitute (plugs for coconut shell containers and orifices of prepared human corpses).

• Pillows• Model canoes• Called Wuj´

• Replaced by styrofoam in modern times!

Drftwood TLS

Laticifer

Unusual features of driftwood

• Parenchyma-like fibres with numerous vestured pits and no intrusive tip growth

• Vestured fibre pits without borders• Very low and narrow rays• Sporadic laticifers in rays• Marginal parenchyma (distinct ring

boundaries!)• Very few and very narrow vessels

Stem and Rootwood of Alstonia spatulata

Lowland swamp forest tree in the Indo-Pacific from Thailand to New Guinea

Ingle & Dadswell 1953

Uses of A.spatulata rootwood

• Pith Helmets• Cork substitute• Rafts

• Trade names include: Siamese Balsa• Rootwood of Alstonia pneumatophora

and Dyera spec. (Apocynaceae) has similar uses

Alstonia spatulata stemwood

Wood Sample of Alstonia spatulata from Tervuren Xylarium

Collected by:

His Majesty King Leopold III of Belgium

Leopold III

Leopold III

Kew Samples of A. spatulata

• Vestured pits present!

• Laticifers – none seen

• Growth rings distinct

Rootwood (above)

Stemwood (below)

Rootwood variables

• Fibre diameter and length

• Ray height and width (1-seriate)

• Vesturing of fibre and vessel pits

• Vessel diameter and frequency

• “Growth ring width”

• Laticifer density (zero to very low)

Functional Speculation

• Growth rings reflect inundation cycles!• Thin-walled tissue & lack of fibre

elongation reflect lack of mechanical function!

• Fibre wall deposition is too limited to complete pit borders of vestured pits!

• Very wide fibres for water storage and/or as subsidiary conducting cells !?

Wood of Swamp Forest Trees in Perspective

• Alex Wiedenhoeft finds comparable patterns in Amazon inundation forest species from 5 different plant families

• Peculiar wood anatomy of Leptospermum crassipes from swamp flats in Australia recalls that of A. spatulata

• Conclusion: xylem structure of swamp trees and shrubs shows convergent adaptation and its development and functions deserve further study.

Leiden “Balsa” wood sample (= A. spatulata!)

Base has rootwood; distal part intergrades towards stemwood

Q to You: How can trees survive on such a mechanically weak and hydraulically unfit base?

“Balsa wood”

Section Alstonia

A. scholaris A. boonei

Monuraspermum

A. spectabilis

Wood Anatomy follows monophyletic sections in Alstonia