ON THE ORIGINS OF THE OVULE AND CUPULE IN LYGINOPTERID PTERIDOSPERMS

Camp, Wendell H., and Mary M. Hubbard. (U. Connecticut, Storrs.) On the origins of the ovule and cupule in Lyginopterid pteridosperms. Amer. Jour. Bot. 50(3): 235–243. Illus. 1963.—The recently described Eurystoma angulare of the Lower Carboniferous with its naked, dichotomously branched, ovule‐bearing branch truss may be taken conceptually as a starting point in a series of evolutionary reductions and modifications involving other known forms which ultimately led to the cupule surrounding the solitary ovule of later lyginopterids. It is postulated that the integuments of these ovules also were derived from dichotomously branched lateral trusses which immediately subtended the primitive megasporangia, but of less complexity than that which produced the cupule. Eurystoma indicates that ovules evolved independently of leaves; therefore, ovules cannot be thought of as having been derived from leaf tissues. Evidence is presented indicating that, although these pteridosperms produced ovules of considerable complexity, they did not bear seeds but dropped the pollinated ovules before fertilization. The already specialized organization of the ovules of the Lower Carboníferous pteridosperms indicates that the group must have originated in the Devonian. The structure of the Lyginopterid ovule is reinterpreted, indicating a basic similarity to that of the angiospermous ovule.