The earliest known botanical collection of
B. sphaerocarpa occurred in December 1801, during the visit of
HMS Investigator to
King George Sound. The specimen was collected from "A single plant observed between
Princess Royal Harbour &
Oyster Harbour on a heath", and is credited to English botanist
Robert Brown, though it is not possible to be certain on this point, as Brown incorporated the collections of junior expedition members into his herbarium without attribution. Neither Brown nor expedition horticulturist
Peter Good mentions the collection in his diary. Brown published a formal description and name for the species in his 1810
On the Proteaceae of Jussieu. He did not designate a
type specimen (a specimen to be representative of the species) for the species, but the one specimen in his collection has since been formally declared the
lectotype for the species. He also did not state the
etymology of the
specific epithet, but it is accepted that the name derives from the
Ancient Greek ("round"), and ("fruit"), in reference to the shape of its infructescences. In
Brown's arrangement of the genus,
B. sphaerocarpa was placed between
B. pulchella and
B. nutans in
taxonomic sequence; that is, an order that places related taxa next to each other. No subdivision of the genus was given, other than to separate a single distinctive species into a
subgenus of its own. Meissner also published a variety,
B. sphaerocarpa var.
glabrescens, based on specimens collected by
James Drummond; this is now considered a synonym of
B. incana. For many years following Bentham's arrangement, the circumscription of
B. sphaerocarpa was widely recognised as unacceptably broad.
William Blackall informally published two varieties, var.
pinifolia and var.
violacea (properly
Banksia violacea) in his 1954
How to Know Western Australian Wildflowers; and in 1966 the nurseryman
Fred Lullfitz predicted that there were as many as eight taxa within the species. Several of these were recognised in George's revision of the genus for 1981 "
The genus Banksia L.f. (Proteaceae)":
B. micrantha,
B. grossa,
B. lanata,
B. scabrella,
B. telmatiaea,
B. leptophylla and
B. incana. George placed
B. sphaerocarpa in subgenus
Banksia because of its flower spike, section
Oncostylis because its styles are hooked, and the resurrected series
Abietinae, which he constrained to contain only round-fruited species. He reduced variety
latifolia to
synonymy with variety
sphaerocarpa, but conceded the species needed further review. George's arrangement remained current until 1996, when
Kevin Thiele and
Pauline Ladiges published an
arrangement informed by a
cladistic analysis of
morphological characteristics. They retained George's subgenera and many of his series, but discarded his sections.
Banksia ser.
Abietinae was found to be very nearly
monophyletic, and so retained. It further resolved into four subclades, so Thiele and Ladiges split it into four
subseries.
Banksia sphaerocarpa appeared in the second of these, initially called the '
grossa clade' for its most
basal member. As with George's classification,
B. grossa and
B. micrantha emerged as close relatives of
B. sphaerocarpa. }} This clade became the basis for new subseries
Sphaerocarpae, which Thiele defined as containing those species with lignotubers, styles loosely curling around the infructescence (although this trait was reversed in
micrantha), and "transversely aligned cells of the seed wing inner face". Other than the most basal
B. grossa, these species also have shouldered follicles. Having found
B. micrantha to be more closely related than
B. sphaerocarpa var.
dolichostyla to the other varieties of
B. sphaerocarpa, they promoted var.
dolichostyla to species rank as
Banksia dolichostyla. Morphological support for this was given by the fact that the old styles of var.
dolichostyla are quite different from those of other varieties, being stouter, and tending not to curl around the infructescence as the others do. Questioning the emphasis on cladistics in Thiele and Ladiges' arrangement, George published a slightly modified version of his 1981 arrangement in his 1999 treatment of
Banksia for the
Flora of Australia series of monographs. He added that he did not feel the characters of
dolichostyla alone justified specific rank, being essentially merely larger in all parts than, but otherwise essentially similar to, var.
caesia. Therefore, he retained it as a variety of
B. sphaerocarpa. To date, George's 1999 arrangement remains the most recent comprehensive classification. The placement of
B. sphaerocarpa in
George's 1999 arrangement may be summarised as follows: Early in 2007, Mast and Thiele initiated a rearrangement of
Banksia by merging
Dryandra into it, and publishing
B. subg. Spathulatae for the taxa having spoon-shaped
cotyledons. They foreshadowed publishing a full arrangement once DNA sampling of
Dryandra was complete; in the meantime, if Mast and Thiele's nomenclatural changes are taken as an interim arrangement, then
B. sphaerocarpa is placed in
B. subg.
Spathulatae. In 2008, George reinstated
B. sphaerocarpa var.
latifolia, and published the new variety
B. sphaerocarpa var.
pumilio.
Varieties Banksia sphaerocarpa is a widely distributed Western Australian species with four (or five if one includes var.
dolichostyla) varieties: •
B. sphaerocarpa var. caesia, first described by Alex George in his 1981 revision of the genus, grows larger than most other varieties, reaching , or occasionally , in height. It has yellow blooms and bluish grey foliage and is found in the central and southern
Wheatbelt between the towns of
Piawaning,
Kojonup,
Newdegate and
Corrigin. •
B. sphaerocarpa var. dolichostyla (Ironcap Banksia) was first described by Alex George in his 1981 revision of the genus. It is the largest of the varieties, encountered as a large shrub or small tree to high. It is larger in all parts than the other varieties, and has been considered a separate species. It is restricted to a small area from South Ironcap, east of Hyden, south to Mt Holland in the eastern Wheatbelt. •
B. sphaerocarpa var. latifolia was originally described in a manuscript by Mueller and published by Bentham in 1870. It grows as a small rounded shrub to in height, and is restricted to the vicinity of the south coast between
Denmark and the
Porongorup Range, where it is found in low, open forest of
Eucalyptus marginata and
E. calophylla. •
B. sphaerocarpa var. pumilio, first described by Alex George in 2008, is a small shrub less than a metre high. It is found from
Tathra National Park east of Eneabba south to the Chittering valley. Its subspecific name is derived from the
Latin "small", relating to the flowers. •
B. sphaerocarpa var. sphaerocarpa is widely distributed from the
Darling Plateau east of Perth to the
Whicher Range in the southwest, and southeast to the
Stirling Range. Populations north of Perth once referable to it are now classified as var.
pumilio. File:Banksia sphaerocarpa caesia Bendering.jpg|var.
caesiaBendering Reserve |alt=Closeup of spherical golden yellow bloom made up of hundreds of individual flowers File:Banksia dolichostyla email.jpg|var.
dolichostyla File:Banksia sphaerocarpa var. pumilio gravelpit Cataby flower.jpg|var.
pumilioin gravelpit near
Cataby ==Distribution and habitat==