Compared with Gymnospermae pollen, the fern spore has 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。