Thanks very much, Garg ji, for surfacing this Zingiber cernuum VS nimmonii.
Considering they are different species, we need to see sufficient observations from the field experts; so that we can easily differentiate them.
I think they are not easily differentiated visually when we see the plant in the fruiting phase OR with dehisced fruits.
Shrikant ji Ingalhalikar's
Further Flowers of Sahyadri,
the second among the three field guides to identify plants of northern Western Ghats of India, based on flowers, have photos of both plants:
Zingiber cernuum: page 380
Zingiber nimmonii: page 397
My observation of the Zingiber cernuum illustrated at FOI, agrees well with the illustration in Shrikant ji's FFOS.
But, all this could be wrong, and corrections will need to be done at all places.
Saroj ji,
Clicking on the link you provided takes us to a page showing a flower photographed by one of our friends Sushant More.
On that same page, clicking on "View more" leads us to a page showing two more photos of flowers, looking different.
Both observations - Sushant's and mine - need to be validated by experts.
Sushant had discussed Zingiber nimmonii with me; he said most of the plants of nimmonii in Western Ghats are wrongly identified as cernuum.
I have requested him to write an article or paper about this myth, based on which I can shift IDs of my observations to nimmonii.
Regards.
Dinesh