Alpine plants are well adapted to environments with extreme conditions – low temperatures, a short growing season, increased air humidity and precipitation, and are therefore of particular interest for research. The aim of the present study is to reveal the main reproductive characteristics of two endemic species of the family Campanulaceae, namely Campanula orbelica (Balkan endemic) and Jasione bulgarica (Bulgarian endemic). The main features of the reproductive biology (embryological features, type of reproduction) were established based on the study of micro- and macrosporogenesis and the development of male and female gametophytes. The established features of the reproductive structures and processes characterized C. orbelica and J. bulgarica as sexually reproducing species. Despite the extreme conditions of existence, the studied species presented normal generative progresses leading to the formation of pollen and embryo, which ensures their successful reproduction, populations stability and their distribution in the subalpine environment. In addition, the genome size of C. orbelica was studied by flow cytometry. The estimated genome size varied in the range 1C = 1.34–1.38 pg. No deviation in the ploidy level was found in 22 specimens fresh leaves of which were collected from different parts of the Rila and Pirin Mts.