A. ANNUA — A. KLOTZSCHIANA. 103 



ECOLOGY AND USES. 



Artemisia annua is an annual with a taproot, which occurs in America as a naturalized 

 weed in waste places, and in fallow fields, where it forms a consocies of the secondary 

 succession. 



It is probable that this species is not sufficiently abundant at any place in America 

 to be of much interest either as a weed or as a cause of hay-fever. It may be held in 

 check by the methods described under A. biennis, but the process may be simplified 

 because of the annual duration of the root. 



14. ARTEMISIA KLOTZSCHIANA Besser, Linnaea 15:107, 1841. Plate 10. 



An annual herb from a taproot, 5 to 10 dm. (or more?) high, the odor not known; 

 stem simple below, strictly erect, striate, conspicuously canescent, reddish where the 

 tomentum has been rubbed off; basal leaves crowded, short-petioled, less than 2 cm. 

 long, bipinnately divided into filiform segments, canescent; upper leaves 1 to 2 cm. 

 long, once or twice pinnately parted or divided into linear-filiform segments, gray with 

 a dense somewhat villous tomentum; inflorescence a compound terminal spike nearly 

 as long as the whole plant, short-leafy throughout, 20 to 50 cm. (or more?) long, about 

 2 cm. broad, or much broader when composed of ascending spike-like branches; heads 

 heterogamous, sessile or subsessile, erect; involucre hemispheric, 2.5 to 3 mm. high and 

 slightly broader; bracts 12 to 18, all elliptic, green beneath the canescent tomentum 

 save for a narrow white-scarious border; ray-flowers 50 to 70 (?), fertile, corolla narrowed 

 above, less than 1 mm. long, granular; disk-flowers 6 to 12, fertile, corolla campanulate, 

 about 1 to 1.3 mm. long, 4- or 5-toothed, granular; style-branches of ray-flowers acute, 

 of disk-flowers truncate at the penicillate summit; mature achenes not seen. 



Mexico, from Coahuila and San Luis Potosi to Vera Cruz and Hidalgo; also in Ecuador. 

 Type locality, plains of Perote, Vera Cruz. Collections: Saltillo, Coahuila, Palmer 87 

 (Gr); San Luis Potosi, Schaffner 706 (NY, US); city of Zacatecas, Palmer 784 (Gr); 

 near Zontecomate Station, Hidalgo, Pringle 8918 (Gr, NY, UC, US); Pachuca, Hidalgo, 

 Purpus 1566 (NY, UC). 



RELATIONSHIPS. 



There is little doubt that this species is closely related to A. biennis, notwithstanding 

 its very different appearance due to the remarkably dense gray pubescence. The leaves 

 are much smaller in the present species, the involucral bracts are narrower and less 

 scarious, and the achenes are slightly smaller and probably less distinctly angled. It is 

 not impossible that the disk-achenes both in klotzschiana and annua are partly sterile, 

 whereas they are normally all fertile in biennis, but this opinion requires more material 

 before it can be verified. The exceptionally large number of ray-flowers, that is, 54 to 

 68 in the plants examined, is unique, but the number will doubtless be found to be more 

 variable as further collections are studied. 



There is a wide gap between the geographic area occupied by this species and that of 

 A. biennis. It is not surprising, therefore, that a number of minor morphological dif- 

 ferences can be found, as noted above, and that there are no intermediate forms as to 

 pubescence. It is possible that klotzschiana is an offshoot from A. vulgaris through 

 subspecies wrighti, which it much resembles in superficial appearance, but from which 

 it differs in floral characters, the large number of ray-flowers, and especially in the very 

 different root-system. 



The extension of range of this species southward to Ecuador is on the basis of a single 

 specimen at the New York Botanical Garden collected by Rose. Further field explora- 

 tion will be necessary to determine whether it is a native so far south or whether it has 

 been introduced from Mexico. 



