MORPHOLOGY OF HIGHER PLANTS. 389 



showy, looking like petals (petaloid), as in the water arum (Fig. 

 263), the common dogwood; Bougainvillea and Poinsettia seen 

 in greenhouses. 



The Torus constitutes the terminal portion of the flower 

 axis or stalk, and is usually more or less conical and somewhat 

 enlarged. When the torus is of this shape the parts of the flower 

 are inserted upon it in serial succession, all of the other parts 

 arising below the pistil. It may, however, be modified into a 

 hollow or cup-like structure which grows up around the ovary, 

 carrying the other parts of the flower (sepals, petals, and stamens) 

 with it, thus changing the relative position of the parts, although 

 it should be understood that the ovary occupies practically the 

 same position in the two cases. 



When the torus is of the first type and the other parts of the 

 flower are inserted below the ovary, the flower is said to be hypo- 

 GYNOUS, as in the orange flower (Fig. 78, A) and the ovary 

 superior ; but when the toriis forms a cup-shaped receptacle and 

 the other parts of the flower arise on its margin above the ovary, 

 the flower is called epigynous, as in the clove (Fig. 78, B ; 223 C) 

 and the ovary inferior. In other cases a ring of leaf-like tissue 

 arises from the torus, forming a cup-like receptacle or tube which 

 is known as the perianth tube, the sepals, petals, and stamens being 

 inserted on its margin. The perianth tube may be free from the 

 ovary, when the flower is said to be perigynous and the ovary half 

 inferior or half superior, as in cherry (Fig. 223, 5) ; or in the 

 case of an epigynous flower it may form a prolongation of the 

 cup-shaped torus. 



Prefloration or estivation is the arrangement of the parts of 

 the flower — more especially the calyx and corolla — in the bud. 

 Some of the terms used in this connection are also employed in the 

 study of vernation. The following are some of the terms which 

 are employed : Valvate, when the sepals or petals meet each 

 other at the edges, as in Malvaceae; imbricated, when the sepals 

 or petals overlap each other, as in the Magnoliace?e ; plicate or 

 PLAITED, when the divisions are united and folded together, as in 

 the petals of Convolvulus and Datura. 



The sepals and petals do not necessarily possess the same 

 arrangement, as in the Onagracese, where the sepals are valvate 



