1152 CARDUACEAE 



mm. long, sparingly ciliate : heads drooping, sessile : bracts of the involucre cuneate, 3 

 mm. high, ciliolate : corolla 2 mm. long ; lobes spreading or recurved. 

 In swamps and low ground, Mississippi and Louisiana. Fall. 



6. Iva microcephala Nutt. Annual, glabrous or nearly so, slight. Stems erect, 

 3-9 dm. tall, much branched above, the branches slender, erect or ascending : leaves often 

 alternate ; blades narrowly linear, 2-5 cm. long, acute, entire, or slightly toothed : heads 

 numerous, sessile or nearly so : bracts narrowly linear to linear- filiform, surpassing the 

 heads : involucres 3-6-flowered, campanulate, 2 mm. high : bracts oblong to cuneate, 

 obtuse to retuse at the apex : fructiferous flowers 3 : corolla nearly 2 mm. long : achenes 

 about 1 mm. long. 



In dry pine lands and waste places, Georgia and Florida. Summer and fall. 



7. Iva angustifolia Nutt. Annual, strigose or hirsute-strigose. Stems erect, or as- 

 cending, 5-12 dm. tall, branching above : leaves various ; blades linear or linear-lanceolate, 

 4-6 cm. long, or the upper 2-4 cm. long, narrowly linear or linear-filiform, acute, entire 

 or sparingly toothed, ciliate : heads numerous, often crowded : bracts narrowly linear or 

 linear-filiform : involucre turbinate, 3 mm. high, bristly : bracts partially united into a 

 cup, the free portions ciliate : fructiferous flowers solitary : corolla 3 mm. long ; lobe, 

 ovate, acutish, recurved : achenes cuneate-obovate, 3 mm. long. 



In river bottoms, Arkansas to Louisiana and Texas. Spring to fall. 



8. Iva xanthiifolia (Fresen.) Nutt. Annual, bright green. Stems erect, 0.5-2 m, 

 tall, much branched, glabrous below, pubescent or merely puberulent above : leaves chiefly 

 opposite; blades broadly deltoid, ovate to lanceolate or elliptic above, 3-nerved, 8-16 cm. 

 long, acuminate, coarsely and irregularly dentate, truncate to cuneate at the base, canes- 

 cent or pale-puberulent beneath ; petioles as long as the blades or shorter above : heads 

 nearly sessile, 2-3 mm. broad, in panicled spikes : bracts of the involucres in 2 series, the 

 outer broadest below the middle, the inner broadest above the middle : staminate flowers 

 10-15 : fructiferous flowers usually 5, with rudimentary corollas : achenes cuneate, usually 

 5, fully 2 mm. long, striate. 



In moist soil or in waste places, Northwest Territory to Michigan, Wisconsin, the Indian Terri- 

 tory, New Mexico and Utah. Summer. 



FAMILY 2. CARDUACEAE Neck. THISTLE FAMILY. 



Herbs or rarely shrubs, or sometimes trees in the tropics, with watery or 

 resinous, or rarely milky sap. Leaves opposite or alternate, sometimes all basal, 

 without stipules. Flowers perfect, pistillate or neutral, or sometimes monoecious 

 or dioecious, aggregated on a receptacle, surrounded by an* involucre. Recep- 

 tacle naked or scaly, smooth, pitted or honey-combed. Involucre of distinct or 

 partially united bracts in one or several series. Calyx of bristles, awns, or 

 scales, or crown or cup-like, forming pappus at maturity, or wanting. Corolla 

 of 5 partially united petals, 5-lobed or in the case of the marginal flowers of the 

 head the corolla is often produced on one side into a ligule ; when ray-flowers 

 are present the head is said to be radiate, when wanting it is said to be discoid. 

 Androecium of 5 stamens partially adnate to the corolla tube : anthers often ap- 

 pendaged at the apex and sometimes at the base, united into a ring (syngene- 

 cious) except in Kuhnia. Gynoecium 2-carpellary. Ovary inferior, 1-celled. 

 Stigmas of the fructiferous flowers 2. Ovule solitary. Fruit an achene. Seed 

 erect. Endosperm wanting. 



A. Perfect flowers with regular corollas. 



Stigmatic lines at the base of the stigma or below the middle. 



Stigmas filiform or subulate, hispidulous. TRIBE I. VERNONIEAE. 



Stigma more or less clavate, papillose-puberulent. TRIBE II. EUPATORIEAE. 



Stigmatic lines extending to the tip of the stigma or to the appendages. 

 a. Anthers without elongated appendages at the top. 



Anther-sacs tailed at the base. TRIBE IV. INULEAE. 



Anther-sacs not tailed at the base. 

 Receptacle naked. 



Bracts of the involucre well imbricated. 



Stigmas of the perfect flowers with terminal appen- 

 dages. TRIBE III. ASTEREAE. 

 Stigmas of the perfect flowers with truncate or hairy 



or papillose tips. 



Bracts of the involucre herbaceous. TRIBE VI. HELENIEAE. 



Bracts of the involucre dry and scarious. TRIBE VII. ANTHEMIDEAE. 



Bracts of the involucre little if at all imbricated, except 



when the broad outer ones overlap the inner. TRIBE VIII. SENECIONEAE. 



Receptacle chaffy. 



* Bracts of the involucre herbaceous, sometimes foliaceous. TRIBE V. HELIANTHEAE. 



