LXXV. COMPOSITiE. 



311 



Thejloieers are moreover said to be 



Ofthi disk, where they stand in or near the centre of tlie head; 



Of the ray, when they stand in the outer circle or circumference of the head; 



Ligulate (strap-shaped), when the limb is split on one side and spread open in the form of a strap. 



Tubular, when they are monopetalous with a regular limb. The heads are termed 



Homogamous, where they consist wholly of perfect flowers ; 



Hetero^amous, where the flowers of the disk are perfect or staminate, while those of the ray or margin 

 are pistillate or neutral ; 



Radiant, where the flowers are all ligulate, as in the dandelion ; 



Radiate, where tliose of the ray or margin only are ligulate, the rest being tubular, as in Aster; 



Discoid, where all the flowers are tubular, as in the thoroughwort ; 



Moncecious, where the same head has both staminate and pistillate flowers ; 



Hcterocephalous, where the same individual plant has some of its heads wholly of staminate, andotheta 

 wholly of pistillate flowers. 



Diacimis, where the same species has some of its individuals with staminate heads only, and othera 

 with pistillate heads only. The anthers are usually appendicuiate, that is, prolonged at Uie summit into 

 a membranous appendage. The achenia are termed 



Rostrate, when they aie prolonged at the summit into a slender neck supporting the pappus, as in the 

 dandelion ; 



Compressed, when they are flattened parallel with the diameter of the head ; 



Obcompressed, when flattened parallel with the circumference of the head. 



FIG. 47.— 1. Helianthus strumosus— head radiate. 2. Vertical section of the head, showing the scales 

 of the involucre, and a single disk-flower remaining upon the convex receptacle. 3. A perfect disk-flower 

 magnified, showing the achenium, the 2 awns of the pappus, the 5-toothed tubular corolla, the 5 stamens 

 united around the branched style, and the chaff-scale at base. 4. Head (radiate) of Solidago cjEsia. 

 6. A pistillate, ligulate flower of the ray. 6. A perfect disk fl. 7. A (radiant) head of Taraxacum Dens- 

 leonis. 8. A perfect, ligulate fl. 9. Achenium, with its long beak and plumose pappus. 10. A (radiant) 

 head of Nabalus altissimus. 11. A flower. 12. Lappa major, head discoid. 13. A flower. 14. One of 

 the hooked scales. 15. A (discoid) head of Eupatorium purpureum. 16. A flower. 17. Ambrosia arte- 

 misiaiblia, 18. Staminate head enlarged. 19. Pistillate involucre enlarged. 20. The fertile flower. 



Conspectus of the Genera. 



S Leaves alternate. . . . § 1 

 } Corollas cyanic. { Leaves opposite or verticillate. § 2 



f discoid. < Corollas yellow §3 



i Leaves alternate. . . . § 4 



C Rays yellow. . i! Leaves opposite or all radical. §5 



I < 5 Leaves opposite or all radical. §6 



radiate. ( Rays cyanic. . < Leaves alternate. . . . §7 



Heads Lradiant. 5 8 



27 



