A few things to discuss. This weekend the NC Native Plant Society Reid Chapter and the Traingle Land Conservancy are sponsoring a "Green Garden Tour". Four local gardens will host visitors during the tour, and the Blomquist Garden is one of them. For more info, visit this link.
We had a great tour last week in the Blomquist Garden. Our topic was "Wild Gingers of the Southeast", and a great crowd enjoyed a lively discussion of the interesting botanical history of these species. I mentioned that I would include some info about the walk in a post, including the 1957 article written by Dr. Blomquist concerning how taxonomically unique were the north american wild gingers. Indeed, professor Blomquist is noted as an expert on the subject of our wild gingers, and this article helped spawn widespread acceptance at the time concerning the validity of the genus Hexastylis. Included here is an excerpt from Doctor Blomquist's article. I apologize for the weird things that happened when I added the article to the post as far as line spacing, etc.
Vol. 8, No. 4, pp. 255-281 BRITTONIA January 9, 1957
A REVISION OF HEXASTYLIS OF NORTH AMERICA*
H. L. BLOMQUIST
"Heartleaves" is the common name of a group of low, perennial, aromatic,
evergreen, herbaceous plants related to wild gingers (Asarum L.) with which they
have generally been considered to be congeneric. Because of their distinctness
as a group, however, from wild gingers of North America, Bafinesque (1825) segregated
these plants from Asarum into a new genus Hexastylis. This segregation
was for a considerable time disregarded by American taxonomists, but in 1903
Small adopted Hexastylis for this group of plants in the first edition of his Flora
of the southeastern United States. This recognition of gexastylis as a genus distinct
from Asarum has not, however, been followed by some of the other taxonomists,
such as Feruald in the 8th edition of Gray's Manual of botany (1950).
Up to the present time, 10 species of this group have been described from
eastern North America, all restricted to the southeastern United States. The only
other region where similar plants occur is in the Orient, and most of these have
been placed in the genus Asarum, where they are still retained. Just how and to
what extent these Oriental plants show relationship to Hexastylis is somewhat
uncertain, since no thorough, comprehensive study of them has been made, as
well as no monographic study of the genus Asarum, beyond the extent of such
treatments as are found in de Candolle's Prodromus (Duchartre 1864) and Engler
and Prantl's Die nat~dichen PfTanzenfamilien (Schmidt 1935, Solereder 1893).
Aside from disagreement as to the generic distinctness of Hexastylis from
Asarum, there is considerable diversity in the taxonomic treatments of heartleaves
in the various floras of those areas in which they occur. Furthermore, all
these treatments are more or less inadequate or even erroneous. This unsatisfactory
taxonomic status of the group is largely due to the differences in degree of
understanding of certain taxa, differences in emphasis, and lack of appreciation
of the relative taxonomic value of certain characters.
in general, in attempting to distinguish taxa, within groups, too much emphasis
has been placed on some structures which are too variable. This is especially
true of leaf-blade form. This varies to such an extent in the population of
one taxonmand often as much on one individual plant--that some leaves may
have the identical form of those of another taxon. It seems, therefore, unfortunate
that form of leaf-blade has been used as much as it has in the naming of species,
such as H. arifolia, callifolia, and heterophylla. Actually, the last epithet applies
to most of them. Another means of distinguishing certain species has been based
too much on the relative sizes of flowers and their parts. These vary to such an
extent that size differences are often of limited diagnostic value. On the other
hand, certain structures, which seem to be more specific and constant, have
apgarently been overlooked by American taxonomists. These are: (1) the pattern
of variegation of the leaf blades, (2) the flare in the calyx-tube of several species,
(3) the extent of the division of the style-extensions above the stigmas, and
(4) the relief pattern inside the calyz-tube present in several species.
In this study, the author has made an effort to examine as many specimens as
possible in living or preserved condition since he has found that in pressed
specimens the flowers of these plants are generally so distorted that it is often
difficult if not impossible to interpret their form and structure unless they have
been seen living or preserved. Besides his own collections, some 1600 specimens
from various herbaria have been examined. Expression of deep appreciation is
due for the courtesy and cooperation of the curators of those herbaria from which
loans of specimens have been obtained.
The first species named of the plants included in Hexastylis was collected in
eastern Virginia by John Clayton before t730 and briefly described in a polynomial
by Gronovius in his Flora virginica (1739). This was later named Asarum
virginicum by Linnaeus in Species plantarum (1753). The next species was discovered
in South Carolina by Andr6 Michaux who named it Asarum arifolium in his
Flora boreali-americana (1803). The third was collected in the southern Appalachians
(Broad River, North Carolina) by Rugel in 1841 and distributed as Asarum
(Monotropa) macranthum, a manuscript name by Shuttleworth. This plant had undoubtedly
been seen also by Michaux, who wrote below his description of A.
virginicum (F1. Bor.-Am. 1:279), "Obs. Folia maculata. Legi varietatem flora
maximo, plus quam pollicari, caetero omnino similem." In 1893, Small and Vail
renamed this species A. grandi/lorum by elevating a varietal name applied to it by
Duchartre (1864), which he accredited to Michaux. But, soon discovering that
this combination became a homunymn, Small (1894) renamed it A. macranthum.
However, in 1897, while studying some specimens of Asarum from North Carolina
and Tennessee sent them by Ashe, Britten and Baker discovered that the name
macranthum was also a homonymn and renamed it A. shuttleworthii (1898). In
1897, Small described another species which he named A. callifolium. This plant
had been collected in Florida at least half a century earlier by Chapman, who had
identified it as A. arifolium Michx. Also in the same year, Ashe described four
new species (,4. rutttii, A. memmingeri, A. heterophyllum, A. minus), but admitted
that A. minus was Irobably the same as A. virginicum. In 1924, Roland M. Harper
discovered a remarkable species in south central Alabama, which he called
258 Brittonia [VOL. 8
Hexastylis speciosa. This seems to be an endemic since it has not been found
elsewhere. The last species to be described was discovered in southeastern
Virginia by Fernald and Lewis and named A. lewisii by Femald in 1943.
The genus Asarum, including those plants segregated as Hexastylis, has
generally been placed in the family Aristolochiaceae, although this name was
preceded by the name Asaraceae. The former name has, therefore, been proposed
for conservation over the latter. However, in 1903, Small recognized the priority
of the family name Asaraceae for the genera Hexastylis, Asarum, and Aristolochia
in his Flora of the southeastern United States. In the subdivision of the family
Aristolochiaceae, Spach (1841) seems to have been the first to divide it into
tribes, of which the tribe Asareae included Asarum. This tribal name was elevated
to the rank of subfamily (as "suborder") by Duchartre (1864). The latest
comprehensive classification is that of Sehmidt in the second edition of Engler
and Prantl (1935), who retains the tribe Asareae but places this under the subfamily
Asaroideae together with two other tribes.
Regarding the infrageneric classification, above that of species, Braun
(1816) divided Asarum into three sections, segregating the species now included
in Hexastylis, together with a few Oriental species, into section Ceratasarum. In
1842, Asa Gray, in emending the genus Heterotropa of Morren and Decaisne (1834)
so as to include A. arifolium and A. virginicum, placed these species in a new
section, Homotropa. Since the generic name Heterotropa was based upon a Japanese
plant, it has not generally been adopted for the North American species, nor
the sectional name Homotropa. Duchartre adopted the sectional names of Braun
and added another (Aschidasarum). This sectional classification was followed by
Solereder (1893) in the first edition of Engler and Prantl. In the second edition of
this work, Schmidt (1935) elevated the sectional name Ceratasarum to the rank of
subgenus and retained it also as a sectional name under this taxon.
Since disagreement exists among taxonomists on the generic distinctness of
Hexastylis from Asarum, it seems necessary to discuss this question. Like specific
concepts, generic concepts are formulated on the basis of personal experience
and judgement. There is, however, a general understanding that if related
groups of species differ in the same way in certain more or less fundamental
characters, they may be segregated as genera, provided there is no serious intergradation
in these characters between such groups. The difficulty in this matter
is, of course, the necessarily subjective evaluation of the fundamentality of
characters. This ultimately rests to a great extent upon phylogenetic considerations
which vary in lime depending upon the acquisition of new facts, and may
vary in application to different groups.
That the two groups of species in southeastern North America which have
been segregated into Hexastylis and Asarum are generically distinct is generally
agreed. The basis for disagreement is to what extent they intergrade in the Oriental
forms. Unfortunately, as is stated above, the Oriental forms are still so imperfectly
known that it is uncertain to what extent any of them are similar enough to
the North American forms to be classified into either of the above genera or both,
and how many can be so treated; and, if both are represented, to what extent and
in what characters, if any, they intergrade.
From what has been seen of the Oriental species, it is fairly obvious that at
least some of them, such as .4. variegatum Braun & Bouche, A. maximum Hemsl.,
A. macranthum Hook. f., and even A. sieboldii Miq. could very well be placed in
Hexastylis. The only characters in which some of them may show some intergradation
with Asarum are mainly vegetative, such as the evergreen vs. annual
habit of leaves, one or more leaves borne on the same branch each season, and
the extent of hairiness of leaves and the outside of the calyx. On the other hand,
similarities are in characters of more fundamental importance, such as the separate
styles with the style extensions above the stigmas, and the partial inferior.
ity of the ovary. In these characters, there seems to be little, if any, serious intergradation.
It must he admitted, however, that a thorough, monographic study of
the Asarum complex may alter our present concepts, but it may safely be assumed
that any such alteration will tend to establish more genera rather than fewer.
So far as North American material is concerned, as is stated above, there
seems to be no question that Hexastylis and Asarum represent distinct genera, as
may be seen from the following comparisons:
Styles united except at the apex, the
stigmas terminal on the spreading lobes.
Ovaries wholly inferior.
Vestiges of petals sometimes present.
Stamens with long filaments.
Anther-connective extending in a long,
Lobes of calyces more or less attenuated.
Calyces hairy on outside.
Two leaves borne each season.
Leaves persisting only one season.
Styles separate, extending above the
Ovaries superior to partly inferior.
Vestiges of petals absent.
Stamens with very short filaments or the
Anther-connective at most extending in a
short, blunt appendage.
Lobes of calyces not attenuated.
Calyces glabrous on outside.
One leaf borne each season.
Leaves essentially glabrous.
Leaves persisting more than one season.
It goes on, but I can't cut and paste drawings and taxonomic keys very well into this blog.
If you want to read the whole thing, find a PDF online for the journal Brittonia, Volume 8 Number 4 from Jan 9, 1957. The article is entitled "A Revsion of the Hexastylis of North America" by H.L. Blomquist
For a simpler introduction to our native wild gingers, here's a short link with a list of the native wild gingers of the southeastern United States.