Fusiform Parenchyma Cells in the Young Wood of Pinaceae, and their Distinction from Marginal Parenchyma

Abstract

Fusiform parenchyma cells found in several genera of Pinaceae are described and compared with marginal parenchyma. Fusiform parenchyma cells are mostly fusiform in shape, with occasional smooth horizontal walls. They form discontinuous tangential bands in complete or incomplete circ1es in the innermost growth rings of Larix, Abies, and Tsuga. Fusiform parenchyma always contains resinous material, and is more conspicuous in branchwoods than in stem woods. Marginal parenchyma cells were observed in Cedrus, Keteleeria, Pseudolarix, and Pseudotsuga as well as in Larix, Abies, and Tsuga, and very rarely in Picea. Marginal parenchyma cells are scattered along growth ring boundaries. They are always in strands with nodular horizontal walls with conspicuous simple pits. Cell wall structure of these two types of parenchyma differs in the intensity of the birefringence of the secondary walls. Fusiform parenchyma cells are distinct from marginal parenchyma with which they were previously confused, and should be regarded as a new component of coniferous wood.