COMPOSITE 337 



and work inwards towards the centre, in this way, 

 the outer, older florets, often catch on their styles, 

 pollen brought from a different flower-head and a 

 different plant. 



This is a beautiful instance of a special mechanism 

 for offering pollen to bees and for receiving later on 

 from bees any they may in turn bring from some 

 other plant, or failing this for securing pollen that 

 may have fallen from the anther of the same flower. 

 And it is one which can be made out very easily, 

 at every stage, in one flower-head. 



COSMOS KLONDYKE the yellow Cosmos of our gar- 

 dens, and COSMOS BIPINNATUS, the pink and white 

 Cosmos, have flower-heads built up in the same way, 

 but different in details. The bracts of the involucre 

 are in two rows, the lower outer row green and 

 spreading, the inner scarious and erect. 



GAILLARDIA, COREOPSIS, ZINNIA and many other 

 common garden plants, having florets massed together 

 in one head, belong to this family. The cultivated 

 Chrysanthemum differs in having many circles of 

 ligulate or ray flowers, but this is the result of culti- 

 vation. 



Some of the family e.g. VERNONIA, EUPATORIUM, 

 CENTRATHERUM and the Thistle have no ligulate 

 florets, all being alike tubular, so that the flower- 

 head has no rays. 



There are others such as NOTONIA, SENECIO, 

 *TARAXUM the Dandelion, Chickory, LAUNEA (fig. 25) 

 and * PICRIS in which all the florets are ligulate, so 

 that there is no separation into disc and rays. 



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