What is "ischnostemma"

Ischnostemma is a genus of flowering plants of the family Apocynaceae, first described as a genus in 1908. It is native to Southeast Asia.

1. Ischnostemma carnosum (R.Br.) Merr. & Rolfe - Luzon Island in Philippines
2. Ischnostemma selangorica King & Gamble - Selangor in Peninsular Malaysia (possibly the same species as the first one, in which case I. carnosum is the correct name)