194 Observation of the Origin of J\irictics. 



cxcliKle(i l)v tlic sterility of the more perfectly double 



l)lants. 



Let us uow l)rielly suuiniarize the results of this ex- 

 perinient. There is, on the market, a 21 -rayed race of 

 the normally 13-rayed Chrysanthcnunn scgctwn. It is 

 not strictly pure, but can easily be made so; it bears the 

 name C. scgctum grandiflornni. From a plant which, 

 in lcS95, caught my attention by a few 22-rayed lateral 

 flowers, I succeeded in raising, by a process of selection, 

 a hitherto unknown race with double flowerheads, the 

 new C. scgctum plenum (Plate II). The course of this 

 process is exhibited in Fig. 32, p. 181, in which tlie 

 X X X X indicate the individuals selected as seed- 

 parents for each succeeding generation. C. scgctum 

 plciuim behaves with regard to its double character, 

 exactly like the double commercial varieties of other 

 species of the same genus (C inodorum, C. indicum etc.). 



The new variety was therefore obtained by bringing 

 to light a character latent in C. scgctum grandifJorum. 



§ 19. DOUBLE FLOWERS AND FLOWERHEADS. 



The experiment described in the foregoing section 

 (^ 18) justifies an attempt to form some conception of 

 the manner in which this phenomenon of ''doubling," 

 which is widely distributed among cultivated composites, 

 may have arisen in other cases. If we examine the facts 

 closely we shall discover in the majority of cases an 

 extraordinarily close agreement with our own specimen, 

 at least so far as the absence of scientific observations 

 admits the possibility of a comparison. 



There are, it is true, certain abnormal types of ''doul)- 

 ling," such as the de\'elopment of secondary flowerheads 



