BOTANICAL INTRODUCTION 45 



The calyx is chiefly used as an organ of protection for 

 the flower bud. Its individual parts are termed sepals. They 

 are usually coloured green; but occasionally the calyx becomes 

 brightly coloured, and usurps the functions of the corolla. Calyx 

 and corolla together constitute the perianth. Sometimes 

 there is only a single ring (whorl) of parts in the floral 

 envelope, or both rings may be similar. In such cases the 

 floral envelope is termed simply a perianth. Flowers without 

 a perianth are said to be naked. If, however, it is clear that 

 the perianth is either calyx or corolla, but not both, the more 

 definite term may be employed. The missing whorl is thon 

 described as suppressed or obsolete. Any leaf on a flower stalk 

 not belonging to the perianth is termed a bract. 



THE DISPERSAL OF SEEDS. 



After the seed is ripe, it has to be scattered. Many curious 

 devices are used by plants to accomplish this end. The seeds 

 may be so light or so small as to be blown about by the wind. 

 They may be provided with down (e.g., as in the dandelion), to 

 assist them in travelling before a breeze. Sometimes they are 

 set in mucilage (as in Pittosporum) . This may enable them 

 to cling to passing animals, and so to be carried for longer or 

 shorter distances ; or, again, they may be provided with hooks 

 for the same purpose, (as in the sedge Unrinia), or with a 

 grapnel-head, (as in Accend). Again, the whole fruit may 

 become sweet and succulent, and thus birds are attracted to it, 

 and eat it The seeds then pass through the digestive 

 canals of the birds, and are distributed over the country 

 by them. The elder, gooseberry, flowering-currant, etc., 

 are thus being distributed by birds over New Zealand. 

 Should the seed on the other hand fall to the ground 

 immediately below the parent plant, it would very 

 likely be choked in the struggle for existence, or might 



