HOW FLOWERS CLUB TOGETHER. 143 



had little or no calyx, the sepals having been con- 

 verted into tiny feathery hairs, used to float the 

 fruit (as in thistledown and dandelion), about 

 which we shall have more to say in a future chap- 

 ter. They had a corolla of five purple petals, com- 

 bined into a single tube. Inside this again came 

 five united stamens, and in the midst of all an in- 

 ferior ovary with a divided stigma. Hundreds of 

 different kinds of composites now existing on the 

 earth retain to this day, in the midst of the great- 

 est external diversity, these essential features, or 

 the greater part of them. 



You may take thistle as a good example of the 

 composite flowers in an early and relatively simple 

 stage of development (Fig. 36). Here the whole 

 flower-head resembles a single large purple blos- 

 som. To increase the resemblance, it has below 

 it what seems at first sight to be a big green calyx 

 of very numerous sepals. What is this deceptive 

 object ? Well, it is called an involucre, and it really 

 acts to the compound flower-head very much as 

 the calyx acts to the single blossom. The florets 

 having got rid of their separate calyxes, the flower- 

 head provides itself with a cup of leaves (tech- 

 nically called bracts), which protect the unopened 

 head in its early stages, and serve to keep off ants 

 or other creeping insects exactly as a calyx does 

 for the single flower. Inside this involucre, again, 

 all the florets of the thistle are equal and similar. 

 Each has a tiny calyx, hardly recognisable as 

 such, made up of feathery hairs which cap the 

 inferior ovary. Within this fallacious calyx, once 

 more, the floret has a purple corolla of five petals, 

 united into a tube. Then come the five united 

 stamens, and the pistil with its divided stigma. 

 This is the simplest and central form of compos- 



