Examples of Constant Races. 
79 
amples of this are the Discoidca forms of many com- 
posites. 
MOOUIN TANDON regarded the Discoid 'ea, i. e., the 
*** fj 
form without tongue-florets, as the Peloria of the Com- 
posites. 1 They are generally regarded as having arisen 
from the Radiata forms. Sometimes the discoid form is 
Fig. 8. Senecio Jacobaea L. (/. radiata}. 
commoner than that with rays, and then the Discoidea 
form may be found described in systematic works as a 
species and the Radiata as the variety ; as for instance in 
Bldcns tripartita (Fig. 7), and B. cernua, 2 although B. 
1 Teratohgie vegctale, p. 179. 
2 KOCH, Synopsis Florae Gcrmanicae, p. 309. 
