558 THE STRUCTURE OF ECONOMIC PLANTS 



lentum, var. cerasiforme, the type investigated by Warner, the form 

 L. esculentum, var. pyriforme, is also pentamerous with a bilocular 

 ovary. 



ANATOMY 



Ontogeny of the Flower. — The floral primordium first 

 appears as a dome-shaped enlargement which is directly continuous 

 with the main axis, and its parts develop in acropetal succession. 



Fig. Z94. A-I, stages in floral development : B, stage showing origin of sepal primordia ; 

 C, more advanced stage showing primordia of sepals and petals ; D, origin of stamen pri- 

 mordia ; E, origin of carpel primordia ; F, G, and H, longisections of flower buds showing 

 advanced stages in development of stem axis in relation to carpels ; I, longisection showing 

 united carpels and development of style : ax, stem axis ; car, carpel primordium ; ov, ovule ; 

 pet, petal primordium ; se, sepal primordium ; sfa, stamen primordium ; sty, style. (Redrawn 

 after Warner.) 



(Fig. X94, A.^ Peripheral enlargement and rapid cell division of 

 this protuberance result in the formation of a somewhat raised 

 blunt ridge at the margin of the primordium. This is followed by 

 accelerated growth on the ridge at five or more equidistant points, 

 and the resultant outgrowths constitute the sepal primordia. 

 (Fig. 194, JB.) These arise in a clockwise direction; and by the 

 time the cycle is complete, the first sepal lobe is somewhat 

 advanced. The growth of the sepal primordia is more rapid on 

 their abaxial sides so that the free tips incline toward each other 

 as they elongate and partially enclose the cavity beneath them. 



