A textbook truism about the poor ferns being held back by a weak link in their life cycle may not be so true after all.
The upright bursts of fronds that we think of as ferns produce unferny offspring in the form of bits of free-living, filmy, green tissue. In a pattern of alternating generations, these scraps of green create gametes that give rise to new fronds.
Gametophytes, typically the size of a fingernail and only one cell thick, get portrayed as "wimpy little delicate things," says James E. Watkins Jr. of Harvard University. Their need for wet environments has supposedly hampered fern species' spread into dry habitats.