Abstract
Cytological study was conducted in the intraspecific and interspecific crosses of Tulipa gesnerlana and T. fosterlana. The fertilization occurred in 5 days after pollination, that is, 5 to 7 days after anthesis when the emblryo sacs were developed to the 8 nuclei. This slow fertilization may be associated with the slow maturation of the embryo sacs or the long styles which may cause the retardation of the pollen tubes to reach the micropyles. The study of the chromosome numbers of the developing embryos and endosperms revealed that in the emblryo sacs the 4 nuclei at the micropylar end were haploid, while the 4 nuclei at the chalazal end were diploid. Triple nuclear fusions of a male gamete and two polar nuclei did not occur to form the endosperm. The endosperms were formed mostly from the development of a single polar nucleus or the double nuclear fusions of a male gamete and a polar nucleus. The difficulty of the interspecific crosses was due to poor development of the endosperms and incompatibility between the embryos and endosperms. In the interspecific crosses between T.gesneriana Niphetos (2X) and T, fosteriana Red Emperor (2X), two seeds were triploid and another one was diploid. It was suggested that some of the interspecific crosses between T.gesneriana and T.fosteriana may often produce triploid seeds because, the triploid Darwin Hybrids had been produced from the same interspecific crosses besides the result of this observation.
