APOSPORY. Apospory is the natural complement of apogamy (q.v.). It may be de fined as the production of a gametophyte from a sporohyte (see ALTERNATION QF GENERA TIONS) without the intervention of a spore. The word means that the spore has been left out. Apospory was first discovered in the com mon bracken fern (Pteris aqui/Ina), where it occasionally appears as an interesting freak. Tissue near the border of the leaflet, which normally develops sporangia containing spores, rows out into thin ribbon-like structures bear ing some resemblance to ordinary gameto phytes (prothallia). These structures bear the antheridia or archegonia or both, which give rise to the sperms and eggs, and, therefore, con stitute a sexual generation. A transverse sec tion of a normal leaflet of the bracken fern bearing normal sporangia (s) is shown in Fig. 1; while Fig. 2 shows a leaflet in which pro thallia (p) with antheridia (a) have developed instead of sporangia. A comparison of the two figures shows that apospory• is a cut) in the life history, since, normally, a spore in the sporangium would have given rise to the prothallium. In some ferns, under moist con ditions, the tips of the leaflets may develop into prothallia bearing archegonia and antheridia.
In a few ferns, the first leaf of the young sporeling, if bent over and brought into con tact with moist soil, may produce prothallia along its border. Other instances of apospory in ferns might be cited, but no case has yet been reported for lycopods or equisetums. Apospory occurs in liverworts and mosses, but is not common, and no case has been proved in Gymnosperms. In Angiosperms there are several cases, including the common dandelion, in which the egg-bearing generation (embryo sac) does not develop from a normal spore and we must admit that apospory is present. All these plants, however, develop their embryos from eggs without fertilization and, conse quently, are apogamous, as well as aposporous. This type is so closely associated with Parthen ogenesis (q.v.) that it well may be considered under that heading.
Bibliography.— Bower, F. 0., The Origin of a Land Flora) (London) ; Lang, W. H., On Apogamy and the Development of Spor angia upon Fern Prothallia) (Philosophical Transactions, Royal Society of London, Vol. CXC, 1898, p. 189) ; Yamanouchi, S., amy in Nephrodium> (Botanical Gazette, Vol. XLV, 1908, p. 289).