THE EVOLUTION PROCESS 237 



the organic expenses of the onset of the 

 reproductive function necessarily check the 

 vegetative ones. 



Similarly for flower groupings, the "forms 

 of inflorescence." The simplest form is the 

 long flowery stem, each flower with its own 

 stalk, like the foxglove spire; but such fine 

 "racemes" are comparatively uncommon. 

 Often the flower-stalks are arrested, and we 

 have the "spike," as in the mullein, golden- 

 rod; or again it may be the main stem which 

 stops short, leaving the minor stalks to grow 

 and separate the flowers, as in the "umbel" 

 of cowslip (and even primrose), of ivy and of 

 the parsley and hemlock tribe without num- 

 ber. But in one great order, and that sig- 

 nificantly one of the most successful in the 

 whole world-flora, the daisy and dandelion 

 order, the axis of inflorescence is arrested in 

 growth until it is a flat disk, and the flower 

 stems have disappeared altogether, so that 

 we have the crowded "head" of flowers, 

 their own individual development greatly 

 reduced, so characteristic of the Composites. 

 This principle of flower-heading is constant 

 in not a few orders otherwise widely distinct, 

 like willows and plantains; and appears here 

 and there among other orders, e.g. in sea- 

 pinks, and even among labiates and rose- 

 worts. It is noticeable that such forms, like 



