The best soil for the Ranunculus is a loam or clay in which the common field Buttercup grows freely and plentifully.
"The Culture of Vegetables and Flowers From Seeds and Roots, 16th Edition" by Sutton and Sons
The type of this is a common British plant, most nearly related to the field buttercup.
"Hardy Perennials and Old Fashioned Flowers" by John Wood
They are daisy and buttercup women of earth Who grace common ways with their sweetness and worth.
"Three Women" by Ella Wheeler Wilcox
It is either solitary, or several achenia may be placed on a common receptacle as in the buttercup.
"The New Gresham Encyclopedia. Vol. 1 Part 1" by Various
There is a tendency to variation even in the common buttercup.
"Wild Life in a Southern County" by Richard Jefferies