. Botanical gazette. Plants. 470 BOTANICAL GAZETTE [December elongation is variable, as is also the height and the depth of the cell, which latter, however, approximates that of the ray with which it is associated. The pitting on the walls is very characteristic, espe- cially in horizontal contact with the parenchyma cell of the ray. Second, the interspersed type of ray tracheid, as shown in fig. 2, where the tracheary cells occur in the midst of the radial prolonga- tion of rays one cell high. They may be found singly, or in groups separated from other cells or groups of cells of similar stru
. Botanical gazette. Plants. 470 BOTANICAL GAZETTE [December elongation is variable, as is also the height and the depth of the cell, which latter, however, approximates that of the ray with which it is associated. The pitting on the walls is very characteristic, espe- cially in horizontal contact with the parenchyma cell of the ray. Second, the interspersed type of ray tracheid, as shown in fig. 2, where the tracheary cells occur in the midst of the radial prolonga- tion of rays one cell high. They may be found singly, or in groups separated from other cells or groups of cells of similar structure by one or more parenchyma cells. Fig. 2 shows two tracheid cells occurring together with parenchymatous ray cells on either. Fig. 3.—Radial section (second growth wood) showing most common form in which vertical wood tracheid is bent and prolonged along the ray to act as ray tracheid; note diversity of pitting in walls of tracheary cell. side. In these the pitting is very characteristic, especially in the radial end walls. Miss Holden has spoken of such rays as these as "secondary ; X In contrast to the foregoing, the marginal structures on the rays of the wood of second growth 5. washingtoniana show great variation. True ray tracheids in accordance with the previous descriptions do not occur. On the margins of the rays, however, there is a peculiar adaptation in the termination of the vertical wood tracheids directly at the ray, with the development of com- municating pits in the contiguous walls of the tracheids and the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hanover, Ind. : J. M. Coulter
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