158 



GROWTH AND WORK OF PLANTS 



acuminate, and in the flower bud the edges fit closely, giving the 

 bud an elongate, four-angled, pointed form. These calyx lobes 

 are the free parts of the sepals, the edges of which are united below 

 to form the tube. As the flower opens the calyx lobes part, and 

 become inverted, hanging downward from the apex of the tube. 

 250. The corolla is bright yellow and consists of four petals 

 which are inserted on the edge of the calyx tube. Each petal 



is broadly wedge-shaped and 

 notched in the free end, or 

 rather it is heart-shaped. The 

 petals are convolute in the bud, 

 as shown in fig. 117, where they 

 are just unfolding. 



251. The stamens are eight 

 in number, seated also on the 

 edge of the calyx tube and partly 

 on the base of the petals which 

 is shown by the fact that the 

 stamen sometimes remains at- 

 tached to the base of the petal 

 when that is removed from the 

 calyx tube. Four of the stamens 

 are set opposite the petals and 

 four are alternate with them as 

 shown in the photograph of 

 a dissected flower in figs. 115, 116. The filaments are strongly 

 curved at the base, all in the same general direction, with the 

 concavity toward the axis of the spike. The anther* consists 

 of two pollen sacs (locules) which open by a long slit on the inner 

 faces. This takes place before the flower opens and the pollen 

 is deposited in great masses on the outer surfaces of the four 

 lobes of the stigma. The stigmatic surface is on the inner face 



* The anthers are versatile, i.e., each anther is attached by one face near 

 the middle to the point of the filament, upon which it swings loosely. The 

 filament is attached to the outer face of the anther, so that the anther faces 

 inward toward the axis of the flower, and is said to be introrse, or incumbent. 



Fig. 115. 



Flower of evening primrose (CE. biennis) 

 with corolla tube split open to show the 

 long style. 



