These are the differences given in Factsheet:
Rubber vine (Cryptostegia grandiflora) is very similar to a closely related species that is known as purple rubber vine (Cryptostegia madagascariensis ). It is also relatively similar to the garden plant known as purple allamanda (Allamanda blanchetii). These species can be distinguished by the following differences:
Re: completed insertion of identified species of Cryptostegia : 1 post by 1 author.
Cryptostegia (Apocynaceae) page with images of species in efloraofindia : 1 post by 1 author.
Pl. go through Cryptostegia (Apocynaceae) page with images of species (done by … & me) in efloraofindia.
If you find any mis-identification, pl. let us know. If anybody can send images of other species of this genera (for incorporation in the website), if any, it will be really nice.
Also, if anybody is interested to take up the activity of inserting images on efloraofindia pages from efloraofindia posts, pl. let us know.