The Structure and Reproduction of Caloglossa leprieurii

The costate, ribbon-like axes of Caloglossa leprieurii have a dome-shaped apical cell, which by transverse division cuts off segments posteriorly. Each segment cell undergoes division into a central cell and four pericentral cells. The two lateral pericentral cells are produced before the two transverse pericentral cells, and in the usual delesseriaceous fashion give rise to lateral rows of cells which form the monostromatic wings of the thallus. The axes are monopodial and the primary, apically (exogenously) produced branches are alternately arranged on the axes. Secondary, endogenously produced branches are also formed. One such branch usually develops at each node and usually emerges on the dorsal (upper) surface of the thallus. Occasionally, an endogenously produced branch also issues from the midrib of an internode. At the nodes are also formed rhizoids which are usually initiated by the ventral (lower) pericentral cells. The sexual plants are usually dioecious, but in rare instances they are monoecious. The spermatangia are formed in sori which develop on the wings of the thallus on both sides of the midrib and simultaneously on both surfaces of the terminal and subterminal internodes. Procarps are produced in acropetal succession by the transverse pericentral cells in the terminal parts of the thallus. Generally, they are formed on the ventral surface, but not infrequently they also occur on the dorsal surface, and at times they are produced on both surfaces of an internode. In general, the development of the procarp and cystocarp is like that in other Delesseriaceae. However, the carpogonium of Caloglossa forms a connecting cell. This is a primitive feature which heretofore has not been observed in any of the many genera of Delesseriaceae that have been studied. The tetrasporangia are generally produced in the tips of the tetrasporophytes. The sporangia are formed by the cells of the wings of the thallus. Each cell forms only one sporangium. After the sporangium has been initiated, the remaining portion of the mother cell divides by two periclinal walls to form a cover cell on each surface. The present study supports Kylin's placement of Caloglossa in a separate group within the Delesseriaceae. Taenioma is here removed from the Sarcomenia to the Caloglossa group. The question of the systematic position of the Sarcomenia group (which was recently transferred to the Rhodomelaceae by Womersley and Shepley) is discussed in some detail. It is concluded that it would be incorrect to place the members of this group anywhere else than in the Delesseriaceae, where they occupy a position seemingly not far removed from the Claudea and Caloglossa groups.