THE FLO WEE 



115 



223. Union of unlike parts, or adnation. Frequently the stamens 

 seem to grow from the corolla, because the filaments have grown 

 to the petals (Figs. 160, 161). Again, in the flower of Cuphea, for 

 example, calyx, corolla, and stamens adhere in a cup around the pistil, 



160. Flower of a Primrose laid open; 

 co, corolla ; ca, calyx. 



161. Flower of Cuphea laid open ; 

 ct, calyx tube ; pt, petals. 



in such a manner that both stamens and petals seem to be inserted on 

 the margin of the calyx tube (Fig. 161). Finally, in the Purslane 

 (Fig. 162) all the different members are united, with the ovary in the 

 center. The ovary is in such cases said to be inferior. When free 

 from the organs, it is superior (Fig. 160). The adherence of unlike 

 members is termed adnation. In the Purslane, for example, the calyx 

 is said to be adnate to the ovary. 



Coalescence and adnation come about in the following manner. 

 The rudiments of the carpels, stamens, petals, and sepals appear at 

 first as minute elevations on the young receptacle. As these increase 

 the surface of the receptacle between them may be involved in the 

 growth. Thus, if the tissue between 

 the nascent petals is affected, a cir- 

 cular ridge arises, upon the edge of 

 which the position of the original 

 petal rudiments is indicated by prom- 

 inences. The ridge, or ring, grows up 

 into a longer or shorter tube (the 

 corolla tube), the original prominences 

 becoming lobes or divisions. By a 



similar process, in the Primrose (Fig. 160) the rudiments of the 

 stamens become united to the corolla ring at an early stage. In 

 the Purslane (Fig. 162) a single ring arising from the receptacle, 

 and bearing all the floral organs on its summit, comes to form the. 

 so-called "calyx tube.'* 



162. Flower of the Purslane. 



