Seal of Imperial Throne- Chrysanthemum
 

I am interested in the background story of the chrysanthemum seal of the emperor, since 797.
I should like to know what species is recognized as form after which this art work was designed. Probably, Chrysanthemum indicum, and not Chrysanthemum x morifolium.
I am searching for an article which explains this. The emperor has an emblem with 16 petals, it seems that other members of the imperial family use a 14-petal seal.
I hope somebody can help me finding a scientific article in English on this. Thanks.