406 PLANTS OF NEW ZEALAND 



flowers and seeds are remarkably constant. This is, doubtless, 

 due to the fact that the contrivances employed for pollination 

 and seed-distribution, though comparatively simple, are yet 

 highly efficient. The family may be contrasted in this respect 

 with the Orchidaceae, (q.v.). In spite of there being many 

 and most complex adaptations for pollination among the 

 orchids, yet their flowers are often sterile, and species have to 

 rely for survival upon the occasional production of large 

 numbers of seeds in a single capsule. In the Composites, on 

 the other hand, each pistillate floret produces only one seed^ 

 and many florets are abortive. Nevertheless, some of the 

 species {e.g. dandelions, thistles, etc.) are amongst the most 

 abundant weeds known. No plants are more often victorious. 

 in competition with their rivals, or better adapted for offensive 

 warfare. 



The chief contrivances by which the success of the family 

 has been procured are the following. The involucral bracts 

 replace the calyx, and protect the flower-head as a whole in 

 the bud, and also as a rule bend up and enclose the young^ 

 fruit. The sex of the florets varies in different species. 

 Commonly, however, the ray florets are pistillate, and the disk 

 florets hermaphrodite. Not infrequently, however, the florets 

 of the ray are sterile, and therefore only of value in attracting 

 insects. The first obvious gain in the massing together of the 

 flowers in heads is conspicuousness. Another advantage is 

 that insects may pass from flower to flower without loss of 

 time. 



Cross-pollination is thus effected in the family. Honey is 

 secreted by a ring of glands round the base of the style. When 

 the flower opens, the style-arms are closed. The stamens 

 ripen first, and the pollen falls upon, and is carried up by the 

 still growing style through the anther ring. Any insects now^ 

 visiting the flower must come in contact with it on entering, 

 and remove some of the pollen. Finally, the arms of the style 

 expand, and expose the now mature stigmas. Should these 



