Helianthus Compositae 971 



surface of the ground. In a few years the space in the bed became occupied 

 and the plants began to crowd. In a bed of Helianthus grosseserratus I 

 measured one plant 9 feet high with an inflorescence 2 feet long while sev- 

 eral other plants in the same bed were but 3 feet high with a single head. 

 In a bed of Helianthus divaricatus which usually has only a few heads I 

 found one with more than 50 heads and some with a single head. I have 

 observed unusual plants in the field. Once I found a whole colony of a 

 species which normally has a simple stem that had branches at every node. 

 In my beds I have cut back plants at different dates to learn what the re- 

 sponse would be and have found it had no perceptible effect upon the 

 degree of pubescence or length of the hairs and little or no effect upon the 

 size, shape, and serration of the leaves. 



Quantitative characters such as pubescence may be quite variable within 

 one species and in another may be quite constant. The shape and length 

 of the involucral bracts vary so greatly in most species that they can not be 

 safely relied upon as characters, although in Helianthus rigidus the in- 

 volucre is constant enough to characterize the species. Ordinarily the color 

 of the plant is very significant although we do have both bluish green and 

 grayish green plants of the same species. The leaves are mostly opposite, 

 in some species more or less alternate, and rarely a specimen with ternate 

 leaves. A study of herbarium material often reveals aberrant specimens 

 which can not be named satisfactorily because the growth environment is 

 not known. I have excluded 15 species that have been reported for the 

 state. For a discussion of these see excluded species. 



Cauline leaves linear, less than 1 cm wide and more than 10 times as long as wide; 



disk flowers red 1. H. angustifolius. 



Cauline leaves ovate, lanceolate or linear-lanceolate, less than 10 times as long as wide. 

 Receptacle flat; annuals; leaves alternate; disk flowers red. 



Heads 1-2.5 cm wide; chaff toward the center of the head conspicuously white- 

 bearded; achenes appressed-pubescent all over at maturity.. .2. H. petiolaris. 

 Heads more than 2.5 cm wide; chaff not white-bearded; achenes glabrous or only 



slightly pubescent at maturity 3. H. annuus. 



Receptacle convex; perennials; leaves mostly opposite or mostly alternate. 



Plants generally with fewer than 7 internodes below the inflorescence; leaves 

 usually large, long-tapering at the base, on petioles mostly 3-10 cm long; 

 inflorescence on vigorous plants paniculate with heads on long peduncles; 



depauperate plants usually with 1-3 heads and often on short peduncles 



4. H. occidentalis. 



Plants not as above, internodes more than 7. 



Corolla lobes of disk flowers reddish, never yellow. 



Bracts of involucre oblong, glabrous on the back; cauline leaves deep green, 

 rounded and blunt at the apex, rarely acute. (See excluded species no. 



659, p. 1100) H. atrorubens. 



Bracts of involucre of an ovate type, usually glabrous on the back, sometimes 

 scabrous, shorter than the disk and appressed; cauline leaves gray green, 



long taper-pointed at the apex 5. H. rigidus. 



Corolla lobes of disk flowers yellow, never dark colored. 



Heads small, the disk rarely more than 7 mm wide; leaves ovate-lanceolate, 

 thin, the lower surface conspicuously resin-dotted; petioles 1-3 cm long; 

 rays 5-7, 1 cm long; usually flowering in August and in early September. 

 6. H. miorocephalus. 



