The presence of corollary corona, sagittate anthers and dumb-bell shaped stigma are the characteristic features of .............

The flowers are bisexual and actinomorphic. The calyx is synsepalous and 5-lobed. The corolla is sympetalous and 5-lobed. The stamens are adnate to the corolla tube (or perigynous zone). The anthers are adherent to the stigma. The gynoecium consists of a single compound pistil of 2 carpels which are united by a single style. Each ovary has numerous ovules on marginal placentation. 5 glands or an annular ring is usually found at the base of the ovary. 
All these characteristic features are observed in Catheranthus roseus.
So, the correct answer is 'Catheranthus roseus'