Compared with gymnospermae pollen, the fern spore has a more closer relationship with soluble organism in the low-rank source rocks from the coal-bearing strata.

• 而蕨类孢子和裸子植物花粉相比，可能对低熟-未熟油，特别是含非烃较高的低熟油有某种更为密切的联系。