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The Role of Wood Anatomy in Phylogeny

1946; University of Notre Dame; Volume: 36; Issue: 2 Linguagem: Inglês

10.2307/2421510

1938-4238

Oswald Tippo,

Plant and animal studies

During the past three decades, plant anatomists have established a number of lines of phylogenetic specialization in the structures of the stele. Just as the taxonomists have worked out certain trends in the evolution of the flowerfor example, the change from spiral to the cyclic arrangement of the floral organs, from free floral parts to fused floral organs, from hypogyny to epigyny, etc.-so morphologists have described the following lines of anatomical specialization: 1. The prostostele is more primitive than the siphonostele or the dictyostele (i.e., eustele of Brebner) (Jeffrey, 1897, 1917). 2. In the Angiosperms, the woody stem of trees and shrubs is more primitive than that of herbaceous plants (Eames, 1911; Sinnott and Bailey, 1914, 1922; Jeffrey and Torrey, 1921, 1921a). 3. The vessel element with scalariform perforation plates appeared in plants before the vessel member with a single opening in the perforation plates (Jeffrey, 1917; Bailey and Tupper, 1918; Frost, 1930, 1930a). 4. Among the vessel elements with scalariform perforation plates, the tvpe with numerous bars and narrow openings is more primitive than the type in which there are few bars separating wide openings or perforations (Frost, 1930a). 5. The vessel elements which are long, small in diameter, and angular in cross-section preceded those which are short, broad, and circular in crosssectional outline (Bailey and Tupper, 1918; Bailey, 1920; Frost, 1930). 6. Vessel elements with long, sloping end-walls are more primitive than those with end-walls which are transverse (Bailey and Tupper, 1918; Frost, 1930, 1930a). 7. The phylogenetic order of the several types of pitting on the side walls of the vessels is scalariform, transitional, opposite, and finally alternate (Bailev and Tupper, 1918; Frost, 1930, 1931). 8. The type of vessel arrangement in which the pores occur singly throughout the wood (i.e., solitary pores) is less advanced than the various aggregate groupings, such as pore multiples, pore clusters, and pore chains (Frost, uinpublished data). 9. The diffuse-porous condition is more primitive than the ring-porous state (Frost, 1930; Gilbert, 1940). 10. Evolution has proceeded from tracheids to fiber-tracheids to libriform wood fibers (Jeffrey, 1917; Bailey and Tupper, 1918; Bailey, 1936). Accompanying this development there has been a progressive decrease in the length of these elements (Bailey and Tupper, 1918; Bailey, 1920). 11. So far as the several categories of tracheids are concerned, the phylogenetic development in the Angiosperms has been from scalariform tracheids to circular bordered pitted tracheids (Jeffrey, 1917). 12. The diffuse arrangement of wood parenchyma cells is more primitive than are the various aggregate arrangements, such as banded apotracheal and