CHAPTER IV 



THE FLOWER, FRUIT AND SEEDLIXG 



50. The Structure of the Flower. — All the energy of the plant 

 is directed towards the perpetuation of its kind. Numerous ex- 

 amples have been noted where this is accomplished by bulbs, 

 rootstocks, buds, etc. Among our common plants, however, new 

 individuals are usually produced from seeds that are formed in 

 the flowers. We will first examine the structure of a flower and 

 see how it is adapted to the performance of this important work. 

 A flower is a highly modified stem of the bud type. This is 

 very noticeable before the flower opens or is in bloom (Fig. 74, 

 A). A series of leaves usually of a greenish color envelop the 

 delicate parts within and protect them, as in the case of the bud, 

 against drying winds. These green leaves are known as the 

 calyx and each individual leaf is called a sepal. As the bud 

 opens a number of organs are disclosed, particularly noticeable 

 are a set of more delicate and variously colored leaves the 

 corolla, each leaf of which is called a petal (Fig. 74, B). The 

 corolla is of service to the flower in many ways. Like the calyx 

 it may assist in protecting the other organs. Especially is it of 

 importance in guarding them against dews and Tains. For 

 this reason the calyx and corolla collectively called the floral 

 envelop or perianth, in many flowers often close at night or on 

 rainy days. It will be seen later in the work that the perianth 

 is of the greatest importance in assisting insects to visit the 

 flowers in such a way that seeds may be produced. Within the 

 perianth are two kinds of peculiar organs, the central flask-like 

 ones are called pistils or carpels and surrounding them are the 

 stamens (Fig. 74, B). These two kinds of organs are collec- 

 tively known as sporophylls since their special work is to pro- 

 duce certain cells called spores. The sporophylls are the im- 

 portant organs of the flower. The calyx and corolla may be 

 lacking but no seed can be formed without the sporophylls. 



