12 



broad base (annuus-style) , upper surface shiny (petiolaris char- 

 acter), the margins remotely and rather feebly dentate; smaller 

 leaves narrower, practically entire; involucral bracts broad but 

 tapering, the margin rather long-ciliate; disc small, 26-28 mm. 

 diameter, dark with in some cases the white-haired center of 

 petiolaris weakly indicated; rays long and ample, 34-42 mm. long, 

 in one or two rows; achenes (immature) delicately hairy all over. 

 When the pollen has come from a red annuus, the chestnut-red 

 color appears in the hybrid, but always (on upper side) at base of 

 rays, forming a very distinct ring or band occupying about the 

 basal quarter of the rays. Thus the color-pattern is unlike that 

 of H. annuus, and resembles rather that of H. cticumerif otitis . 

 On the under side of the rays the middle third shows more or less 

 red, especially on the apical half; there is no relation between the 

 patterns of the upper and under sides. 



This hybrid is obviously not aridus or patens. If those plants 

 are in any sense of hybrid origin, they are certainly not Fi 

 hybrids between petiolaris and annuus. On the other hand, the 

 above hybrid should occur in nature, wherever the two species 

 grow together. In the size of the flower-heads it is intermediate 

 between the parents; in the general mode of growth and shiny 

 leaves it is petiolaris, but the broad leaves with truncate base 

 have the shape of annuus. The petiolaris color-pattern, not 

 before known, is dominant over that of annuus. In all respects 

 the plants are very like the annuus X cucumerifolius crosses pre- 

 viously made, and it is clear that H. petiolaris is a close relative of 

 cucumerifolius. An important character not mentioned in current 

 descriptions of H. petiolaris is the white center of the disc. 

 This is due to the remarkable tufts of white hairs at the ends of 

 the disc bracts, but only on those at and near the center. This 

 character is wholly absent in all H. anmms. In the hybrid it is 

 feebly indicated. 



It is necessary to consider briefly thenomenclatural history of H. 

 petiolaris. Nuttall described it in 182 1 " from the sandy shores 

 of the Arkansa; flowering in August." He notes that the leaves 

 are "somewhat shining and almost destitute of serratures." 

 The achenes are "covered with a silky and fulvous down." The 

 flowers are about 3 or 4 inches in diameter, and the petioles and 

 peduncles are of great length. 



