Dryandra subg. Diplophragma
Dryandra subg. Diplophragma is an obsolete subgenus within the former genus Dryandra. It was first published by Robert Brown in 1830, but was discarded by George Bentham in 1870. It was reinstated with a new circumscription by Alex George in 1996, but was ultimately discarded again in 2007 when Austin Mast and Kevin Thiele sank Dryandra into Banksia.
According to Brown
Diplographma was first published by Brown in his 1830 Supplementum primum prodromi florae Novae Hollandiae. Brown's arrangement divided Dryandra into three groups according to what Brown perceived to be variations in the number of seed separators. He allowed for these groups to be treated at subgenus or section rank, but they are now treated as having been published as sections.D. sect. Diplophragma was defined as containing a single species, D. bipinnatifida, which Brown thought contained two seed separators. The epithet Diplophragma is from the Greek diplo and phragma. It is not clear how Brown came to believe that this species has two seed separators, as it actually has none.
The placement and circumscription of D. sect. Diplophragma in Brown's 1830 arrangement may be summarised as follows:
According to Meissner
In 1856, Carl Meissner published a revision of Dryandra. He retained all three of Brown's sections, but added bipinnatifid leaves to the defining characters of D. sect. Diplophragma, and included in it the species D. preissii, which had been published in 1845. The placement and circumscription of D. sect. Diplophragma in Meissner's arrangement thus looks like this:According to Bentham
Along with many of Meissner's infrageneric taxa, which were overly reliant on leaf characters, Bentham discarded D. sect. Diplophragma in his 1870 arrangement. Despite having seen only a few seeds, he correctly observed that the characteristics of the fruit upon which Brown based the section were not constant: Bentham also recognised that the two species placed in D. sect. Diplophragma by Meissner are not closely related; he placed D. bipinnatifida in D. sect. Aphragma, and D. preissii in D. sect. Eudryandra ser. Niveae.According to George
When Alex George published his revision of Dryandra in 1996, he recognised that D. bipinatifida possessed a number of very distinctive characters, especially in its fruiting structure. These include unusually large follicles and seeds; seeds that are set within the seed wings rather than along the base or one side; and unusual double wings that are attached to each side of the seed. In addition, the species has extremely long involucral bracts, and floral bracts that enlarge more than any other species. Recognising the need for this species to be placed in its own subgenus, George resurrected Diplophragma, promoting it to subgenus rank as D. subg. Diplophragma.The placement and circumscription of D. subg. Diplophragma in George's arrangement, as amended in 1999 and 2005, may be summarised as follows: