CARDUACEAE 



1157 



Bracts of the involucre relativelj* broad, not embracing 

 achenes. 

 Achenes 5-10-ribbed or 5-10-angled. 



Involucre many-flowered : pappus present. 

 Outer bracts of the involucre separate. 

 Outer bracts of the involucre united. 

 Involucre few-flowered : pappus wanting. 

 Achenes flat. 

 ** Bracts of the involucre spreading or reflexed. 



Involucre of subulate or linear bracts : disk-corollas each with 



a very sliort tube and glandular-pubescent lobes. 

 Invohicre of foliaceous bracts without an inner series of hya- 

 line bracts : disk-corollas each with a manifest tube and 

 glabrous lobes, 

 b. Receptacle with bristle-like chaff. 

 B. Plant-tissues, especially the leaves and bracts of the involucre, with oil 

 glands. 

 Bracts of the involucre more or less united : stigmas of the disk-flowers 

 elongated. 

 Bracts of the involucre united at the base. 

 Bracts of the involucre united into a cup. 

 Bracts of the involucre distinct : stigmas of the disk-flowers very short. 



Tribe VII. ANTHEMIDEAE. 

 Receptacle chaffy. 



Achenes terete, at least not flattened : involucre hemispheric : heads large. 

 Achenes flattened : involucre obovoid tocampanulate : heads small. 

 Receptacle naked, or sometimes merely pubescent. 

 Ray-flowers usually present. 



Receptacle flat to hemispheric : bracts of the involucre in several series. 

 Receptacle conic to ovoid : bracts of the involucre in few series. 

 Ray-flowers wanting. 



Heads corymbed : pappus a short crown. 

 Heads spicate, racemose or panicled : pappus wanting. 

 Pistillate flowers with corollas. 

 Pistillate flowers without corollas. 



Tribe VIII. SENECIONEAE. 



Bracts of the involucre lax, the broad outer ones strongly overlapping the 



inner. 

 Bracts of the involucre erect-converging, narrow, not much overlapping. 

 Leaves opposite, sometimes mainly basal : pappus-bristles rigid. 

 Leaves alternate : pappus-bristles soft. 



Corollas white, whitish or pinkish : ray-flowers wanting. 

 Disk-flowers perfect : marginal-flowers pistillate. 

 Disk-flowers and marginal-flowers perfect. 

 Involucre of about .5 main bracts. 

 Involucre of 12-1.5 principal bracts. 

 Corollas yellow : ray-flowers usually or typically present. 



Tribe IX. CYNAREAE. 



Achenes inserted on the receptacle by their bases, not oblique. 



Bracts of the involucre hooked at the tip : leaves not bristly. 



Bracts of the involucre not hooked : leaves bristly. 

 Achenes obliquely inserted on the receptacle. 



Heads not sessile in bristly leaves. 



Heads sessile in bristly leaves. 



Tribe X. MUTISIEAE. 



Corollas essentially regular, deeply 5-lobed : shrubby plants. 



Corollas all bilabiate, or the marginal ones ligulate : herbaceous plants. 



Heads heterogamous. the marginal flowers radiate. 



Heads homogamous, all the corollas bilabiate. 



119. B.\HI.\. 



120. Tetraneuris. 



121. PiCRADENIA. 



122. Flaveria. 



123. Laphamia. 



121. Helenium. 



125. Ambi.yolepis. 



126. Gaillardia. 



127. Boebera. 



128. Thymophylla. 



129. Pectis. 



130. Anthemis. 



131. Achillea. 



132. Chrysanthemum. 



133. Matricaria. 



134. Tanacetdm. 



135. Artemisia. 



136. SOLIVA. 



137. Haploesthes. 



138. Arnica. 



139. Erechtites. 



140. Mesadenia. 



141. Synosma. 



142. Senecio. 



143. Arctium. 



144. Carduus. 



145. Centaurea. 



146. Cnicus. 



147. Gochnatia. 



14S. Thyrsanthema. 

 149. Perezia. 



1. VERNONIA Schreb. 

 Perennial, caulescent herbs or shrubby plants, with upright stems. Leaves usually 

 alternate : blades mostly toothed. Heads discoid, in panicled or corymbed open cymes 

 Involucres hemispheric to cylindric or nearly turbinate : bracts imbricated in several series. 

 Receptacle flat, naked. Corolla regular : lobes 5. Anthers sagittate, not caudate. Stig- 

 mas subulate, hispid. Achenes 8-10-ribbed, truncate. Pappus double, the outer series of 

 scales or stout bristles, the inner of numerous, rough, hair-like bristles. Some of the 

 species are called Iron Weed. The plants flower during the summer and fall, or in the 

 extreme south somewhat earlier. 



A. Leaves mainly or all cauline. 



a. Bracts of the involucre or some of them with filiform or subulate tips. 



Involucres over 15 mm. broad. 1. V. crinita. 



Involucres less than 10 mm. broad. ^ 



Leaf-blades smooth above. 



Pappus purple or purplish. 2. V. Noveboracensis, 



Pappus straw-colored. 



Outer bracts of the involucre filiform or subulate-filifo m. 3. V. tomcTitosa. 



