Boiko I. The Genus Hosta Tratt. in Ukrain (ontogenesis, reproduktive ability, usage).

The thesis deals with complex morphological-biological study of ontomorphogenesis, rhythms of development and reproductive possibility of the species and cultivars of the genus of the Hosta Tratt. in cultivation in Ukraine. The peculiarities of the periods and stages of ontomorphogenesis on the example of the model species H. ventricosa were determined and the considerable peculiarities of the main age states have been revealed. The features of the sprouts development of the H. ventricosa with emphasis on their branching and monocarpic sprout development peculiarities have been considered and the characteristic of the seasonal development rhythms of the three model species (H. ventricosa, H. sieboldiana and H. plantaginea) have been established. The three groups of plants in dependence of terms of flowering were picked out. The relation of the seeds germination depends from temperature and the terms of sowing and storage conditions. The experiments dealing with vegetative propagation on the Hosta plants by the stem grafts of different types: separate rosellate sprouts, separate renewal buds and pats of rhizome with dormant buds were made. The best results were obtained with grafting by rosellate ground sprouts.