pbio 450 Lecture Notes

James L. Reveal

Norton-Brown Herbarium, University of Maryland


Selected Families of Angiosperms: Dilleniidae

Violales Perleb, 1826

Cronquist (1988) defines the order as consisting of 24 families and nearly 5000 species, the bulk of which are found in five families: Begoniaceae (1000 species), Flacourtiaceae (more than 800 species), Violaceae (800 species), Cucurbitaceae (700 species) and Passifloraceae (650 species). He builds the taxon with Flacourtiaceae as his basal group, but in doing so acknowledges that the "Loasaceae, Begoniaceae, Cucurbitaceae, and a few of the smaller families may conceivably prove to belong somewhere else" (p. 339). Recent studies have demonstrated that this is certainly the case.

Takhtajan (1997) defines the Violanae as consisting of several orders, many of which Cronquist also recognizes. Of the families within Cronquist's Violales, however, Takhtajan keeps only a fragment within his Violales, notably Flacourtiaceae, Peridiscaceae, Lacistemaceae, Scyphostegiaceae and Violaceae. Takhtajan removed Bixaceae, Cistaceae and Huaceae to the Cistales in his Malvanae. Thus, except for these three families, the basal core of Cronquist's Violales is basically the same as Tahktajan's.

The next group of families in Cronquist's arrangement, Tamaricaceae and Frankeniaceae, are treated as a related order in the Violanae, the Tamaricales, while the decidedly odd pair, Dioncophyllaceae and Ancistrocladaceae, are each assigned ordinal status and put in the Theanae. Takhtajan puts Turneraceae, Malesherbiaceae, Passifloraceae and Achariaceae in the Passiflorales, and appends the order adjacent to his Violales. The Caricaceae and Fouquieriaceae are each given ordinal status, and while the Caricales remain in the Violanae, the Fouquieriales are transferred to the Ericanae.

The Cucurbitaceae, Datiscaceae and Begoniaceae are also retained within the Violanae by Takhtajan, the first in the Cucurbitales and the second and third in the Begoniales. The decidedly odd family, Stachyuraceae, is assigned to the Theales, and even here it is somewhat odd although Thorne (Aliso 6: 57-66. 1968) first associated the family with the thealian complex in 1968. Today, all concur with his placement. This leaves two families, Hoplestigmataceae and Loasaceae which are disassociated entirely from the Dilleniidae and placed in the Lamiidae; the first in the Boraginales (Solananae) and the latter in the Loasales (Loasanae).

As can be seen, there is considerable disagreement between Cronquist and Takhtajan whose systems are usually regarded as rather similar. When it comes to a comparison between Cronquist and Thorne (1997), differences are expected and present.

Thorne's Violanae are restricted to a single order, Violales, and this is divided into four suborders with much of the same makeup as that of Cronquist's order. For example, both include Violaceae and Flacourtiaceae, the latter defined so as to include both Lacistemaceae and Scyphostegiaceae, and each accepts Peridiscaceae. Like Takhtajan, Thorne removes the bixalian threesome preferring to have them in the Malvales as a suborder, Cistineae. And, of course, both keep Violaceae. Thus, the same basic core of families are retained by all three. Of the more advanced members of the order, Thorne accepts Passifloraceae, Turneraceae and Malesherbiaceae in the Violineae while removing to other suborders the Cucurbitaceae, Begoniaceae and Datiscaceae. Finally, like Cronquist, Thorne retains the two tamaricoid families that Takhtajan puts in the Tamariciales in the Tamariciineae.

However, Thorne departs significantly from Cronquist by including Salicaceae in his Violales, rather than separating the family out as Salicales in an adjacent order. Also, he adds to the order Elaeocarpaceae, a family Cronquist put in the Malvales. In both instances, there is support for either treatment.

The early rbcL data were not particularly informative here as only a few representatives have been examined. Violaceae were associated with the Erythroxylaceae and Chrysobalanaceae, and the Passifloraceae were positioned near the Euphorbiaceae. The Cucurbitaceae, Begoniaceae and Datiscaceae as well as the Tetramelaceae which Cronquist and Thorne put in synonym under the Datiscaceae, fall out as a group next to a clade dominated by members in the Hamamelididae, namely the so-called "lower hamamelids." Clearly the information was useful, but the sketchy pattern it presented could only be regarded as tentative.

My own conclusions do not help clarify the situation all that much, but a few points may be made. I am comfortable with the same, basic core group of families as everyone else accepts, recognizing a few more families here than Cronquist. I prefer to adopt ordinal rank for the more advanced members of Cronquist's Violaceae and near relatives: Passiflorales, Caricales, Salicales, Elaeocarpales, and the Tamaricales in that order. The cistalian families must be placed in the Malvanae, and I prefer to recognize the Cucurbitanae, which I assign at the end of a series of superorders that fall along one line of evolution that goes back to the Theanae. While I do not suggest placement of the cucurbits in the Hamamelididae as suggested by the rbcL data, I believe the group does require recognition at the rank of superorder and must be isolated from the Violanae proper. The overall assessment may be reviewed in the comparison table of the Violales sensu Cronquist.

Flacourtiaceae L.C. Rich. ex DC., 1824

Trees or shrubs; leaves alternate or rarely opposite or whorled, evergreen or deciduous, simple, entire or gland-toothed, stipules mostly small and caducous; inflorescences variable, mostly in racemes or cymes, occasionally solitary, rarely in cone-like heads; flowers small, bisexual or infrequently unisexual, actinomorphic, hypogynous or infrequently perigynous or epigynous, the sepals 3-8 (15), free or infrequently connate basally, imbricate or occasionally valvate, sometimes accrescent in fruit, the petals 3-8 (15) or rarely lacking, free, imbricate, not always clearly differentiated from the sepals; stamens typically numerous, rarely as few as 4, developing centrifugally, free or connate basally, some reduced to staminodes and these rarely forming a corona, the anthers tetrasporangiate and 2-locular, dehiscing by longitudinal slits or infrequently by apical pores, rarely with a prolonged connective; gynoecium superior or rarely inferior, the carpels 2-10, united to form a compound but unilocular ovary with parietal or basal placentation (occasionally seemingly multilocular due to placental intrusion), rarely plurilocular and axile, the styles free or connate but the stigmas always distinct, the ovules 2-many per locule, anatropous to amphitropous or orthotropous, bitegmic and crassinucellar; fruits a berry, a loculicidal capsule or a drupe, the seeds often arillate or even woolly, the embryo straight or rarely horse-shoe shaped, in abundant, oily endosperm; x= 10-12. CA3-8 CO3-8 A-many GSI(2-8). 85 genera and more than 800 species. Mainly tropical and subtropical regions of the world with some temperate representatives in Asia, Africa and the Americas.

I concur with Cronquist (1981) that the Flacourtiaceae represent the basal element within the Violales and is rather well removed from the remaining families as I define the order. Their relationship to the Passiflorales is one of their probably sharing a common, thealian origin. The remaining families in the order are all variously specialized as to habit, pollinator, seed dispersal and gynoecial structure.

From time to time Cronquist (1988) defines a family so as to include a whole series of odd and unrelated genera into what affectionately becomes known as a "garbage pail" family. In short, the "dumping ground" of some order. For his Violales, this is the Flacourtiaceae. He was, and is, not alone in treating the flacourts in this manner as they are without doubt one of the more exascerbating messes in the Dilleniidae. Also, how to dismember them is not clear either, although at the moment, Takhtajan (1997) has removed some of the more obvious, and a few have been taken up by Thorne (1997). Furthermore, some of the genera placed in the flacourts by much earlier authors have, off and on, been moved in and out of the family, most notably to the Passifloraceae.

Over the years, Takhtajan has been trying to define the Flacourtiaceae in a more precise way, and aside from moving some genera elsewhere (e.g., like Cronquist, the Paropsieae and Abatieae to the Passifloraceae), he has established three additional families that seem distinctive, namely Berberidopsidaceae (3 monospecific genera of Chile and eastern Australia), Aphloiaceae (monospecific of eastern Africa, Madagascar and various other island systems in the Indian Ocean), and Bembiciaceae (also monospecific and of Madagascar). Briefly, he separates these as follows:

As defined by Takhtajan, the Flacourtiaceae are restricted to about 80 genera and about 875 species. He subdivides the family into eight tribes: Erythrospermeae DC., Oncobeae Benth., Kiggelarieae DC. (including Pangieae Clos), Homalieae (R. Br.) Dumort., Scolopieae Warb., Prockieae Endl., Flacourtieae DC. and Samydeae (Vent.) Dumort. (including Casearieae Benth.). His family synonymy includes Prockiaceae, Samydaceae, Homaliaceae, Kiggelariaceae and Pangiaceae.

None of the modern workers remove the basically apetalous and perigynous Samydeae out of Flacourtiaceae and into their own family, Samydaceae, as was done commonly in the past. To give a flavor of the problem, I quote Lindley's (Nat. Syst. Bot.: 65. 1836) discussion of the Samydaceae:

This order appears to be of very uncertain affinity. Its apetalous flowers and fruit approximate it to Bixaceae, its dotted leaves to Amyridaceae, near which De Candolle stations it, and its perigynous stamens to Rosaceae, with which its alternate stipulate leaves also ally it. Its fruit, as in Casearia parviflora, is sometimes remarkably like that of Violaceae. In habit the order [=family] approaches Smeathmannia among Passifloraceae. [Robert] Brown observes, that Samydaceae are especially distinguished by their leaves having a mixture of round and linear pellucid dots, which distinguish them from all the other families with which they are likely to be confounded.
Notice that Lindley makes no mention of the Flacourtiaceae, although under that name he states that the flacourts "have some relation to Samydaceae" (p. 70). Both families were put in his Violales.

One of the more distinctive features of the Flacourtiaceae is the unilocular ovary (plurilocular in the Samydeae), and the tendency in some (e.g., Kiggelarieae) to form a corona akin to that found in the Passifloraceae. A quick review of Cronquist's synonymy for Flacourtiaceae will disclose no shortage of names should one wish to disassemble the family. As stated above, Thorne's inclusion of Scytopetalaceae in the Flacourtiaceae is dubious, and while I appreciate the difficulties in placing this family in any linear sequence, I do not come away with the impression that this is a flacourt. Their inclusion makes the definition of the Flacourtiaceae most difficult to defend.

Bixaceae Link, 1831

Trees, shrubs, subshrubs or herbs, with orange or red latex; leaves alternate, simple and entire to lobed or palmately compound, with well-developed stipules; inflorescences in racemes or panicles; flowers mostly mid size, bisexual, actinomorphic or slightly zygomorphic, hypogynous, occasionally appearing before the leaves, the sepals 5, free, imbricate, often quickly deciduous, the petals 5, free, imbricate or convolute; stamens numerous, developing centrifugally, connate basally and seated on a nectariferous disk, the anthers tetrasporangiate and 2-locular, dehiscing by short slits or pores; gynoecium superior, the carpels 2-5, united to form a compound, deeply-lobed ovary with parietal placentation, the styles free short-lobed, the ovules numerous per carpel, anatropous, bitegmic and crassinucellar; fruits a loculicidal capsule, the seeds glabrous or woolly, the embryo straight in abundant, oily endosperm; x= 6-8. CA5 CO5 A(many GSI(2-5). 3 genera and some 25 species. Tropical and subtropical regions of southern Asia, Africa and the Americas.

Placement of Bixaceae (3 species; entire leaves and generally a 2-carpel pistil), and its oft-recognized sister family, Cochlospermaceae (2 genera and about 20 species; palmately-lobed leaves and a 3-5 carpel pistil) has long been problematic. On almost any morphological or anatomical basis one can make an argument for associating these families and the related Cistaceae into the Violales near Flacourtiaceae, the Malvales near Tiliaceae, or into one (Cistales) or two order, the Bixales and Cistales. Contrary to Cronquist's views, the general tendency was to assign the taxon to the Malvanae in a more or less basal position based on wood and seed anatomy. In doing so in 1997, I believed it was necessary to associate with the taxon the family Diegodendraceae as well as two or three other families. This view was shared generally by Thorne (1997) but rejected by Takhtajan who keeps Diegodendraceae next to Sphaerosepalaceae and near both Sarcolaenaceae and Sterculiaceae in his Malvales.

As mentioned under the discussion of the Malvales (see above) the complex of families (Sphaerosepalaceae, Diegodendraceae, Bixaceae and Cochlospermaceae) can be associated into the Bixales with the Cistales actually revised and expanded to include the Muntingiaceae, Cistaceae, Monotaceae, Dipterocarpaceae and Sarcolaenaceae. The only other option is to follow Alverson et al. (1998) and reduce these and the whole of the Malvales to a single order. The most significant point that can be made here is that Bixaceae, Cistaceae and their relatives are not members of the Violales, nor are they related to the Violanae.

Bixa is noted as the source of the orange coloring used for body paint by the indigenous peoples of the tropical Americas. Cochlospermum is occasionally cultivated. I am not aware of any stated uses for any of the three species of Amoreuxia.

Cistaceae Juss., 1789

Shrubs, subshrubs or herbs, with colorless sap; leaves opposite or infrequently alternate or verticillate, simple and entire, sometimes highly reduced and scalelike, with or without stipules; inflorescences mostly cymose, sometimes solitary; flowers small, bisexual, actinomorphic, hypogynous, the sepals (3) 5, free or nearly so, convolute, the petals (3) 5, rarely lacking and then only in cleistogamous flowers, free, convolute or rarely imbricate, often soon deciduous; stamens numerous, sometimes as few as 3 or 6, developing centrifugally, free and seated on a nectariferous disk, the anthers tetrasporangiate and 2-locular, dehiscing by longitudinal slits; gynoecium superior, the carpels 3 (5-10), united to form a compound, typically unilocular ovary with parietal placentation, the styles connate, the ovules (1) numerous per carpel, orthotropous or rarely anatropous, bitegmic and crassinucellar; fruits a loculicidal capsule, the seeds glabrous, the embryo curved or coiled (rarely straight) in abundant, starchy endosperm; x= 5-9, 11. CA5 CO5 A-many GSI(3). 8 genera and approximately 200 species. Temperate and subtropical regions mainly of the Northern Hemisphere.

The Cistaceae, Bixaceae and Cochlospermaceae are better placed in the Malvanae than the Violanae. Takhtajan (1997) divides the Cistaceae into three tribes: Cisteae Rchb., Hudsonieae and Lecheeae Spach.

The largest genus is Helianathemum with about 110 species. Most of 17 species in the genus Cistus are cultivated, with C. incanus subsp. creticus probably the "myrrh" of biblical references. Some, therefore, have a long history of medicinal uses. The genus Hudsonia is restricted to coastal eastern North America; the plant is occasionally cultivate under the name "beach heather" because of its habit and highly reduced leaves. The most difficult genus of the family in eastern North America is Lechea, a taxon of perhaps 15 species that are troublesome to identify and occasionally slightly weedy.

 Violaceae Batsch, 1802

Annual or perennial herbs, shrubs, lianas or small trees; leaves alternate or infrequently opposite, simple and entire to lobed or dissected, with usually persistent stipules; inflorescences of a solitary flower or the flowers aggregated into racemes, heads or panicles; flowers mostly mid size, bisexual or rarely unisexual, actinomorphic or zygomorphic, hypogynous, occasionally cleistogamous and rarely cauliflorus, the sepals 5, free or nearly so, imbricate, persistent, the petals 5, free but the lowermost prolonged into a spur in those with zygomorphic flowers, convolute or imbricate, usually persistent; stamens (3) 5, developing centrifugally, free or connate and often connivent around the ovary, typically with a prolonged membranous connective and some with a nectary in the form of a spurred lower stamen, the anthers tetrasporangiate and 2-locular, dehiscing by longitudinal slits; gynoecium superior, the carpels (2) 3 (5), united to form a compound, unilocular ovary with parietal placentation, the styles connate, the ovules 1-2 or many per carpel, anatropous, bitegmic and crassinucellar; fruits a loculicidal capsule or occasionally a berry or rarely nutlike (Leonia), the seeds often arillate, rarely winged, the embryo straight in mostly abundant, oily endosperm; x= 6-13, 17, 21, 23. CA5 COz5 or CO5 A5 GS(3). About 20 genera and approximately 900 species. Cosmopolitan.

The family may be readily divided into two subfamilies, those with a capsule or berry (Violoideae Burnett, 20 genera) or those with a nutlike fruit (Leonioideae). The latter consists only of the genus Leonia, a tropical genus of shrubs and small trees found in tropical South America; the taxon has been considered a distinct family (Leoniaceae) but not much used over the past 100 years. Thorne (1997) has added a third subfamily (Fusispermoideae) for the genus Fusispermum (3 species) found in southern Costa Rica, and from Panama south through Colombia to Peru.

The more primitive members of the family are woody and possess actinomorphic flowers. The more advanced members are zygomorphic, and while still woody, the more specialized of these are herbaceous (notably the genera Viola with more than 300 species found around the world, and Hybanthus with some 150 species generally of more tropical and subtropical regions). The spurred, lower petal so diagnostic of Viola is even more pronounced in some of the tropical lianous genera such as Corynostylis, Anchietia and Schweiggeria where the flowers take on the appearance of Impatiens.

Several members of the family are used medicinally, especially in tropical regions, and some have a long record of use. The pansy is a violet, and that common name is applied to many other species of the genus Viola that are grown in cultivation. However, the common name "African violet" applies to members of the Gesneriaceae (Asteridae) and not Violaceae.

Next page


Rosidae
Lecture Notes

Posted: 16 Dec 1997; last revised 7 Feb 1999