Asterids: Asteraceae

Asterids Very large, diverse group 10 orders, many families Apomorphies: iridoid compounds sympetalous corolla ovules: one integument and the megasporangium is generally one cell thick

Asteraceae Probably the most evolved of the families Two types of flowers Ray Disk Herbs in our area, but can be trees in tropics Very diverse: 19,000 species world-wide Many flowers on the head inflorescence Old name is compositae – b/c a composite of flowers

Asteraceae Inflorescence a head (capitulum): (usu.) many flowers arising from a compound receptacle, subtended by inflorescence bracts: involucral bracts or phyllaries, collectively termed the involucre. Calyx modified as pappus. Fruit an achene.

Floral Formula

Asteraceae – World-wide

Typical Asteraceae Flower

Cross-section of Asteraceae Flower

More detail on disk flower

Note the chaff – bracts below each individual flower

Fruits are achenes

Sunflower “seeds” = achenes

Echinacea sp. – praire cone flower

Liatris flowers

Close-up of achene fruit with pappus

Taraxacum officinale

Close-up of Taraxacum head

Taraxacum fruits

Close-up of Taraxacum flower

Five types of heads: 1) discoid, with only disk flowers; 2) disciform, with central disk flowers and marginal, eligulate female flowers; 3) radiate, with central (bisexual or male) disk flowers and peripheral (female or sterile) ray flowers; 4) ligulate, with all ray flowers (typically with 5-toothed corolla apices); 5) bilabiate, with all bilabiate flowers.

Acourtia microcephala Bilabiate flower posterior lip anterior lip Acourtia microcephala Trixis californica

Ray flowers (heads ligulate = all rays) ligulate corolla Rafinesquia neomexicana Malacothrix californica

Disk flower: heads discoid disk corolla Chaenactis gabriuscula Psathyrotes ramosissima Palafoxia arida

Disk flowers: heads disciform. (2 types of disk fls. , Disk flowers: heads disciform (2 types of disk fls., same or different heads) male heads female heads Ambrosia chamissonis

Heads radiate: inner disk & outer ray fls. disk flowers ray flowers Encelia farinosa Xylorhiza orcuttii

Some heads are "chaffy" ovary disk flower chaff : bracts subtending flowers Encelia californica

Involucre morphology one whorl two whorls many whorls Senecio vulgaris Coreopsis maritima Encelia californica

Phyllaries spiny & squarrose Involucre morphology Phyllaries spiny Phyllaries spiny & squarrose Circium vulgare Silybum marianum

Pappus: modified calyx

Pappus: modified calyx beak capillary bristles, borne atop "beak" capillary bristles: barbellate capillary bristles: plumose

Asteraceae Because the family is so large, it is divided into two Subfamilies which are then divided into tribes: 12 to 17 in the whole family Aster = Subfamily Asteroideae Six tribes we’ll see Dandelion = Subfamily Cichorioideae One tribe

Tribes of the Aster Subfamily Heliantheae Asterae Anthemideae Senecioneae Gnaphalieae Eupatorieae Cynareae

Tribe Heliantheae – Sunflower tribe Opposite leaves Very resinous Bracts attached to individual flowers (chaffy receptacle) Both types of flowers Sunflower (Helianthus) and Echinacea

Heliantheae

Tribe Asterae – Aster Tribe No bracts at the bottom of individual flowers Example is genus Aster, generally fewer than 20 “petals” or ligulate flowers Similar to above tribe, but without resin Chrysothamnus (Rabbitbrush or chico) Another important genus is Erigeron aka fleabane daisy

Chyrsothamnus sp. rabbitbrush

Erigeron elatior

Tribe Anthemideae – Chamomile Tribe Multiple layers of phyllaries of different lengths Richly aromatic Thin, dry, and translucent (i.e. scarious) bracts surrounding the flower base Artemisia (sagebrush is in this tribe) Achillea, Chrysanthemum

Involucre morphology one whorl two whorls many whorls Senecio vulgaris Coreopsis maritima Encelia californica

Chrysanthemum

Achillea millefolium - yarrow

Tribe Senecioneae – Senecio or Groundsel Tribe Silky pappus around each flower Pappus is usually pure white and very abundant Usually naked receptacle Senecio

Senecio triangularis

Tribe Gnaphalieae – Everlasting Tribe Also has scarious bracts around flower base No ligulate flowers, only tubular flowers Example is cudweed or everlasting (Gnaphalium)

Pussytoes in Gnaphalieae

Tribe Eupatorieae – Boneset Tribe “Baseball bat stigmas” No ligulate flowers Usually naked receptacle Snakeweed, Gutierrezia Liatris, common ornamental

Gutierrezia sarothrae – broom snakeweed

Liatris punctata

Dandelion Subfamily - Cichorioideae The Dandelion Subfamily Strap shaped ligulate “petals” No tubular flowers Dandelions (Taraxacum) Lettuce (Lactuca) Includes Cardueae Tribe

Lactuca serriola – prickly lettuce

Tribe Cynareae or Cardueae (in your book) – Artichoke Tribe Head inside a cluster of tightly compressed bracts Like an artichoke, which is in this tribe, we eat the bracts! No ligulate flowers Many bristles on receptacle (spines inside artichoke) Many thistles are in this tribe, Cirsium and also knapweeds, Centaurea Cynara is artichoke Name for genus Carduus

Artichoke - Cynara scolymus

Cirsium scariosum

Cirsium arvense

Argyroxiphium sandwicense, Silversword endemic toMaui

Argyroxiphium sandwicense, Silversword Maui