APOG'AMY dr6, apo. away from + •yagos, gnaws, a wedding). A name which refers to the fact that a plant which ordinarily comes from a fertilized egg may, under certain con ditions, develop in some other way. It is a general term, used to cover all cases in which the asexual plant does not come from a fertilized egg, without reference to the method of its ori gin. 'Parthenogenesis' is that form of apogamy in which a plant is developed from an egg that has not been fertilized. In other eases of apog amy the new plant is developed in a vegetative way from various other tissues. The phenome non of apogamy has been observed chiefly among the ferns, which seem to respond most readily to the conditions which favor it. Numerous eases have now been observed (hnth among native and cultivated forms), in which the leafy plant arises in various ways directly from the prothallium, without the fertilization or even production of an egg. Among the mosses apog amy has never been observed; that is. there is no reason to believe that the spore-bearing struc ture ever has any other origin than a fertilized egg. Among the seed-plants the phenomenon
has been recorded in a mimber of cases, and has usually been wrongly referred to parthenogene sis. So far as the records go, true partheno genesis has been established in seed-plants only for Antennaria and Alchemilla, genera of Corn posita2, and for Thalictrum, a genus of Ranuneu lace:e. In various other eases, however, in which embryos are known to arise in seeds which have received nothing from the pollen, it is discov ered that the embryo is not developed by the unfertilized egg, but arises vegetatively from va rious tissues of the ovule, just as a bud may develop almost anywhere upon a plant. The fact that a seed contains an embryo is not sure indication that this embryo has developed from the egg. In seed-plants, therefore, the extent of the phenomenon of apogamy is uncertain and difficult to determine.