Characterization of Myriogramme livida, Myriogrammeae trib. nov. (Delesseriaceae, Rhodophyta)

The Myriogramme group of Kylin was found to contain two distinct clusters of genera that merit recognition at the tribal level. In this paper, we establish the tribe Myriogrammeae based on a study of the type species of Myriogramme, M. livida, from the Southern Hemisphere. The Myriogrammeae is characterized by 1) marginal and diffuse intercalary meristems; 2) nuclei arranged in a ring bordering the side walls of vegetative cells; 3) microscopic veins absent; 4) procarps scattered, formed opposite one another on both sides of the blade posterior to one or more vegetative pericentral cells (cover cells) and consisting of a carpogonial branch, a one-/to two-celled lateral sterile group and a one-celled basal sterile group; 5) auxiliary cell diploidized by a connecting cell cut off posteriolaterally from the fertilized carpogonium; 6) gonimoblast initial cut off distally from the auxiliary cell, generating one distal and one to two lateral gonimoblast filaments that branch in the plane of the expanding cystocarp cavity and later fuse to form an extensive, branched fusion cell; 7) spermatangial and tetrasporangial sori formed inside the margin on both sides of the blade by resumption of meristematic activity; and 8) tetrasporangia produced primarily from the central cells. The Myriogrammeae currently includes Myriogramme Kylin, Gonimocolax Kylin, Haraldiophyllum A. Zinova, Hideophyllum A. Zinova, and a possible undescribed genus from Pacific North and South America. Genera are separated based primarily on features of gonimoblast and carposporangial development.