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"Formation of endosperm in the embryo-sac of Agrimonia Eupatorium. Cell-walls are being formed between the nuclei." -Stevens, 1916

A. Eupatorium Cell

"Formation of endosperm in the embryo-sac of Agrimonia Eupatorium. Cell-walls are being formed between…

"Multiple epidermis of leaf of mangrove in cross section. This serves as a water reservoir, and the relatively thick walls of the inner cells reenforce the protective power of the outer layer." -Stevens, 1916

Multiple Epidermis

"Multiple epidermis of leaf of mangrove in cross section. This serves as a water reservoir, and the…

Stages in the development of the elements of the xylem. "B, stages in the formation of tracheids from procambial or cambial cells. The steps are the same as in A, excepting that the cross-walls remain and become pitted." -Stevens, 1916

Xylem Development 2

Stages in the development of the elements of the xylem. "B, stages in the formation of tracheids from…

Stages in the development of the elements of the xylem. "C, steps in the development of wood fibers from cambial cells; 1, cambial cells; 2, the same grown larger in all dimensions with cells shoving past each other as they elongate; 3, a later stage with cells longer and more pointed and walls becoming thickened and pitted; 4, complete wood fibers with walls more thickened than in the previous stage and lignified, as shown by the stippling. The protoplasts in this last stage have disappeared and the fibers are dead." -Stevens, 1916

Xylem Development 3

Stages in the development of the elements of the xylem. "C, steps in the development of wood fibers…

Stages in the development of the elements of the xylem. "D, steps in the formation of wood parenchyma from cambial or procambial cells. 1, group of cambial or procambial cells; 2, the same enlarged in all dimensions; 3, the same with walls thickened and pitted; 4 and 5 show the same stages as 2 and 3, but here the cells have enlarged radially or tangentially more than they have vertically. The walls of these cells are apt to become lignified, but the cells are longer lived than the wood fibers." -Stevens, 1916

Xylem Development 4

Stages in the development of the elements of the xylem. "D, steps in the formation of wood parenchyma…