Polemonium coeruleum. - Blue-flowered. - This is one of the old standard border flowers, and is known by the common name of Jacob's Ladder, from its beautiful pinnately-cleft leaves, (leaflets arranged on each side of a common petiole or leaf-stem ;) its lively blue flowers, nodding, on the ends of the branches. There is another variety with white flowers. Each variety is worthy of a place in the flower department, being perfectly hardy and of the most easy cultivation; flowers in June; two feet high.