382 A TEXT-BOOK OF BOTANY. 



anthers are united, forming a closed ring, and the stamens are 

 spoken of as SYNGENESIOUS (Fig. 222, A) ; in many of the Cucur- 

 bitacece the filaments and anthers both are confluent ; in the flowers 

 of the Orchidacese the stamens are borne upon the pistil and are 

 said to be GYNANDROUS. 



Floral Envelopes. As their name indicates, the floral en- 

 velopes occupy the outermost or lowest position in the arrange- 

 ment of the parts of the flower. In the bud condition they protect 

 the essential elements, and in the expanded flower are considered 

 to play an important role in securing pollination through the 

 visitation of insects. The floral envelopes are made up generally 

 of two kinds of leaves, petals and sepals (Figs. 224 to 227). 



FIG. 222. Union of stamens. A, united anthers of flower of Composite; B, diadelphous 

 stamens of Pisum with i free stamen and 9 united; several types of monadelphous 

 stamens, as in Erythroxylon (C), Melia Azedarach (D), and common mallow (E). After 

 Baillon. 



The PETALS form a spiral which surrounds the andrcecium. 

 They are, as a rule, quite bright and attractive, being frequently 

 highly colored, as in the rose, Fuchsia, violet, etc., and are known 

 collectively as the COROLLA. 



The SEPALS form the next and lowermost spiral. They are 

 usually green and leaf-like, as in the rose and carnation, and 

 together constitute the CALYX. Sometimes the corolla and calyx 

 are spoken of together as the PERIANTH, although, strictly speak- 

 ing, the term has a more special application, and is used mostly in 

 speaking of the sepals and petals of monocotyledonous flowers, 



