FIGURES 144- 152
Subtribe GALINSOCINAE Benth. & Hook., Gen. PI., 2:198, 1873.
*
Alepidocline Blake, *Alloispermum Willd. (in- cluding Allocarpus H.B.K., Calydermos Lag.),*Aphanactis Wedd.,
*
Bebbia Greene, *Cuchumatanea Seid. & Beaman, *Cymophora B. L. Robins., *Dys- critothamnus B. L. Robins., *Faxonia Brandeg.,*
Galinsoga Ruiz & Pavon (including Aduentina Raf., Stemmatella Wedd. ex Benth. & Hook., Sten- ocarpha Blake, Vargasia DC., non Bertol. ex Spreng., Vasargia Steud., Vigolina Poir., Wiborgia Roth, nom. rej., non Thunb.), *Jaegeria H.B.K.(including Aganippea Sesse & Moc. ex DC., Heli- ogenes Benth., Macella Koch), *Otetza La Llave,
*Sabazia Cass. (including Bariasa Steud., Tricarpha Longpre)
,
*Schistocarpha Less. (including Neilrei- chia Fenzl, Zycona 0. Kuntze), *Selloa H.B.K., nom. cons., non Spreng. (including Feaea Spreng., Feaella Blake),*
Tetragonotheca L. (including BikeraNUMBER 51 61 Adans., Gonotheca Raf,, Halea Torr. & Gray, Tetra-
gonosperma Scheele),
*
Tridax L. (including Balbisia Willd., nom. rej., non Cav., Bartolina Adans., Car- phostephium cass., Mandonia Wedd., PtilostephiumH.B.K., Sogalgina Cass.).
Annual or perennial herbs, occasionally shrubs.
Leaves usually opposite, sometimes in basal ro- sette. Heads one to few on short to long peduncles, or in corymbose usually terminal panicles. Heads usually heterogamous; involucre usually subim- bricate, bracts in 2-5 series, coriaceous or some- times herbaceous; paleae present (rare in Alepi- docline), sometimes deeply trifid (in Faxonia, some Sabazia, some Schistocarpha). Ray flowers female;
limb of corolla papillose on upper surface, usually white, usually trilobed at tip. Disk flowers her- maphroditic; lobes of corolla short-triangular, mamillose or papillose on inner surface; anther thecae rather pale to slightly darkened; endothe- cia1 cells subquadrate or oblong, with 1-3 thick- enings on transverse walls (thickenings on vertical walls in a few T r i d a x ) ; anther appendages ovate, with or without glands. Style branches with stig- matic lines paired. Ducts with yellowish resin, ducts usually paired along veins of disk corolla throat, on inner side of veins in lobes and often remote from margin, ducts from adjacent lobes not fused at sinus; usually with two ducts in style inside of veins (4 ducts collateral to 4 veins in style shaft of Oteiza, Schistocarpha, and some Tridax;
4 ducts outside of 2 veins in Tridax brachylepis Hemsl.). Achenes prismatic, walls carbonized, with striations: carpopodium asymmetrical, with hardened plate on outer side, with cushion of soft, collapsing cells on inner side; cells of seed coat irregular with sinuous walls, often strongly orna- mented; apex of achene with distinct callus usu- ally bearing radially disposed bristles or squa- mellae (plumose bristles in Bebbia and T r i d a x ) , pappus sometimes lacking (lacking on ray ach- enes and present in disk in Alloispermum, Faxonia, and some Sabazia). Pollen 23-35 pm in diameter (smaller and apparently nonfunctional in Fax- onia).
T h e subtribe was established by Bentham and Hooker (1873) for members of the Heliantheae
having a terete or prismatic achene bearing nu- merous pappus elements. T h e listing of genera included some extraneous genera such as Balduina, Dubautia, and Marshallia, while close relatives of Galinsoga such as Jaegeria and Sabazia were ex- cluded. T h e only member of the Neurolaeninae included was Calea, but the genus Neurolaena itself was excluded from the tribe. An improved con- cept is evident in the recent publications of Stuessy (1977) and Canne (1978), but the defini- tion remains imprecise. In his key to subtribes, Stuessy emphasizes the conical receptacle and usually translucent anthers, characters that are, at best, unreliable. Steussy includes Spilanthes of the Ecliptinae and Zsocarpha of the tribe Eupator- ieae, but excludes Bebbia and Schistocarpha which are placed in his extremely artificial subtribe Neurolaeninae. Most recently, natural limits have been recognized between Galinsoginae and the Neurolaeninae (Robinson, 1979b), and Schistocar- pha has been transferred to the former, while the
typical element of Calea has been transferred to the Neurolaeninae.
T h e Galinsoginae is regarded here as a totally natural group of Neotropical genera which is represented in the Eastern Hemisphere only by adventive species of Galinsoga and Tridax. T h e subtribe shares many characters with the Neuro- laeninae, but it seems most closely related to the Helianthinae with the characters discussed under that subtribe. T h e extensive development of ducts in the flowers of both subtribes with yellow resin and dehydrofalcarinone polyacetylenes is re- garded a s particularly significant.
T h e prismatic achenes, radially symmetrical pappus, and often subimbricate involucre of the Galinsoginae conform with states held in this study to be primitive in the tribe. In contrast, the reduced, often annual habit of the plants seems more derived. T h e low chromosome numbers in the group, where base numbers over
X
= 10 are lacking, may be a reflection of the trend toward the short-lived perennial or annual habit, but it could be a relict of theX
= 10 that is believed to be basic for the subfamily Asteroideae (Robinson, et al., in press). T h e distinctive, shrubby Dyscri-62 SMMITHSONIAN COKTRIBUTIONS T O BOTANY
PICURES 150- 156.-Galinsoginae-Dimeresiinae-Coreopsidinae: 150, Bebbia juncea (Benth.) Greene, achene, X 12; 15 1, Tridax procumbens L., disk achene, X 12; 152, Dyscritothamnusfilifolius B. L. Robins.. achene, X 8; 153, Dimeresia howellti A. Gray., achene, X 12; 154, 155. Coreopsis lancedata L., disk achenes, X 12 (154, inner surface; 155, outer surface): 156, Bidens pzlosa L.,
disk achene. X 7.
N U M B E R i l 6 3 tothamnus with its achenes densely covered with
“zwillingshaare” is the most divergent element in the subtribe, and may represent a more ancestral habit A chromosome report for the latter would be very instructive.
Limited observations of the surfaces of the ovule indicate potentially useful variations in the subtribe. T h e cells are irregularly shaped and annulately ornamented in Schzstocarpha, in at least one Trzdax, and to a lesser extent in Sabazia lzeb- mannzz Klatt. T h e cells in the equivalent layer in Allozspermum and Sabatia acoma (Blake) Longpre have nearly straight walls and no annulate or- namentation. T h e cells of Selloa are irregular in shape and mostly inornate. In Galinsoga jilformzs Hems1
,
the cells are elongate with closely sinuous walls, and the cells seen in Jaegerza are elongate with nonsinuous inornate walls.Through the kindness of Drs. Ornduff and Strother at the University of California at Berke- ley, it has been possible to make a microscopic examination of the sparing material of Faxonza puszlla Brandeg., an endemic of southern Baja California which is known only from the type specimen T h e immature but well-formed ach- enes lack carbonization, but they show the cor- related punctations in a striated pattern charac- teristic of the Galinsoginae. T h e carpopodium of the ray achenes, the double or even triple resin ducts along the veins of the disk corolla throat, and the ducts inside the veins of the style seem to confirm this placement. T h e trifid paleae of the receptacle and the pappus restricted to the disk achenes find their equal in various other genera of the subtribe. T h e ray corollas of Faxonza are not tubular as represented by Brandegee (1894), but are mostly reduced to a filiform limb. T h e leaves are long-petiolate and mostly narrow-bladed, as originally described.
Some unique features of Faxonza tend to indi- cate an apomictic condition. No stigmatic pa- pillae have been seen on either the ray or disk styles, and the anthers are very reduced and unopened with thin-walled, mostly slightly dis- torted pollen. T h e apparently nonfunctional pol- len grains are unique in their size, usually ca. 15
pm in diameter, although sometimes varying to ca. 20 pm. Grains smaller than 23 pm have been noted otherwise in the Asteraceae only in the tribe Eupatorieae. T h e seemingly defective na- ture of Faxonia might suggest a hybrid origin, but sources for such a hybrid are not obvious and recent origin is not likely. Faxonia seems to be an extremely reduced ephemeral. I suspect a greatly reduced chromosome number with some loss of essential genetic material. T h e genus must have persisted for a considerable time strictly through apomixis.