374 A TEXT-BOOK OF BOTANY. 



IV. OUTER MORPHOLOGY OF THE FLOWER. 



It is well known if the stem of a plant, as the carnation, rose, 

 geranium, etc., be cut into pieces so that each portion has at least 

 one node and placed under suitable conditions for growth, roots 

 will arise from the nodes that are in the ground and a new plant 

 will be developed. The same result can be achieved if plants like 

 Ficus, growing in a greenhouse, have placed around the nodes near 

 the tip of the branches a clump of sphagnum, and if the latter 

 be kept moist roots will arise from the joints. This method of 

 increasing the number of individual plants, while it is limited to 

 certain perennials and cannot be followed with annuals or bien- 

 nials, is frequently resorted to by horticulturists, and is known 

 as vegetative propagation. The production of independent plants 

 in this manner is dependent upon the property of the meristematic 

 cells in the pericycle of the stem to produce the meristems that 

 give rise to the tissues of the root. As this process of propagation 

 for plants growing in temperate regions and in cold climates would 

 be more or less uncertain for the perpetuation of the species, it 

 is fortunate that in Nature safer methods of reproduction are 

 followed, depending upon the development of flowers and the 

 production of seed. In the latter there is a young plant with all 

 of the elements of root and shoot contained therein and so pro- 

 tected by a seed-coat that it may withstand extremes of climatic 

 conditions, as well as the various hostile forces to which it might 

 be subjected. 



The flower is a shoot which has undergone a metamorphosis 

 so as to serve as a means of propagating the individual. It is 

 an unbranched and definite shoot, or an apex of a shoot. It 

 might be termed a " dwarf-branch " that dies and drops ofif the 

 plant after the maturation of the fruit. The most complete 

 flower has four kinds of leaves : sepals, petals, stamens, and 

 carpels. 



The sepals, usually green and leaf-like, make up the outer 

 spiral known as the calyx. The petals being frequently highly 

 colored form an inner spiral known as the corolla. The stamens 

 are the polliniferous organs of the flower, and the carpels bear 

 the ovules which later develop into seeds. 



While the flower is a very complicated structure in many 



