Gentiana cruciata

Gentiana cruciata, the star gentian or cross gentian, is a herbaceous perennial flowering plant in the Gentianaceae family.
Description.
 "Gentiana cruciata" is a hemicryptophyte scapose plant of small size, reaching on average in height. It has erect stems, the leaves are large, ovate-lanceolate, semiamplexicaul, about long. The flowers are violet-blue trumpets with 4 petals, clustered in the axils of upper leaves. The flowering period extends from June to August. The flowers are hermaphrodite and pollinated by insects (entomogamy). The fruit is a capsule. The seeds are dispersed by gravity alone (barochory).
Distribution.
"Gentiana cruciata" is widespread in most of Europe (except Portugal, Great Britain and Scandinavia) and in Western Asia.
Habitat.
This plant prefers dry calcareous soil in forest edges, bushy slopes, pastures, grasslands and dry meadows, at an altitude of above sea level.
Host for "Phengaris rebeli".
"Phengaris rebeli" is an endangered butterfly which feeds upon "G. cruciata." Female "P. rebeli" lay their eggs on the upper side of "G. cruciata" leaves and three to four weeks later, the "P. rebeli" larvae emerge and begin to feed on the seeds and flowers of this grassland plant. After the "P. rebeli" reaches its fourth larval instar, it drops to the ground to be picked up by "Myrmica schencki" ants and brought to their nests.
Female "P. rebeli" prefer to lay eggs on "G. cruciata" growing in clumps rather than individual plants, and on the taller plants, as they are less shaded and allow the eggs to grow and develop faster.