Types of Embryogeny
On the basis of the plane of division of the zygote and of the cells of the 2-celled proembryo, and also taking into account the relative contributions of the cells of the 4-celled proembryo to the mature embryo, six chief types of Embryogeny have been recognized.
A. Division of the zygote is vertical - Piperade type (e.g. Loranthaceae, Piperaceae).
AA. Division of the zygote is transverse.
B. Apical cell of the 2-celled proembryo divides vertically to form a T-shaped, 4-celled proembryo.
C. Basal cell plays no role at all or only an insignificant role in subsequent development of the proembryo-(Crucifer or Onagrad type (e.g., Ranunculaceae, Brassicaceae).
CC. Basal cell and apical cell both contribute to the development of the embryo - Asterad type (e.g., Asteraceae, Violaceae).
BB. Apical cell of 2- celled proembryo divides transversely so that the 4-celled proembryo is usually linear.
D. Basal cell does not participate or only contributes a little to development of embryo proper.
E. Basal cell usually forms a suspensor - Solanad type (e.g., Solanaceae, Linaceae).
EE. Basal does not divide further and the suspensor, if present, is derived from the apical cell - Caryophyllata type (e.g., Caryophyllaceae, Crassulaceae).
DD. Basal cell and apical cell both divide and contribute to formation of the embryo - Chenopodium type (Chenopodiaceae, Boraginaceae).