FORD, C. HEATHER* AND BARBARA CRANDALL-STOTLER. Department of Plant Biology, Southern Illinois University, Carbondale, IL 62901. - A monographic study of the genus Petalophyllum Nees & Gottsche ex Lehm.
Petalophyllum is a simple thalloid liverwort that has been
placed in the family Fossombroniaceae along with three other genera,
Austrofossombronia, Fossombronia and Sewardiella.
In 1844, Lehmann named the genus to include P. preissii
from the Swan River in Australia. Since its naming, there have been
six other species attributed to the genus. With the exception of a
few well-studied localities in the British Isles, Petalophyllum
is poorly known. It has been accepted that this is an important genus
in terms of evolution within liverworts, but its actually position
within the Metzgeriidae is debatable. This study was undertaken to
define species limits and variation potential, determine evolutionary
trends in shoot/sporophyte associations and sporophyte anatomy and
describe biogeographical patterns within the genus. Loans were
obtained from herbaria worldwide and lectotype specimens were
designated. Morphological characters were studied using scanning
electron and optical microscopes and paraffin-sectioning techniques.
Consequently, previous segregation of Petalophyllum along with
Sewardiella into a separate subfamily, the Petalophylloideae,
has been re-evaluated. Of the seven original Petalophyllum
species named, only P. preissii in New Zealand and
Australia, P. indicum in India and Pakistan and
P. ralfsii in Europe and Algeria are maintained.
P. bolivianum, named from Bolivia, was determined to be
Key words: anatomy, liverworts, Metzgeriidae, monograph, Petalophyllum