7.2.Z THE STRUCTURE OF ECONOMIC PLANTS 



flower, there is a floral bract which later encloses the other floral 

 parts. The ovary wall arises as a ring-like fold at the base of the 

 floral primordium, and gradually encloses its apex. (Fig. io6, C.) 

 When the ovary wall has completely overgrown the floral axis, 

 two opposing points on its margin begin to grow more rapidly, 

 initiating the two styles and stigmas. (Fig. io6, E, P".) The 



ax yflv 

 A B 



Fig. io6. A-M, stages in floral development of carpellate flower : A, C, E, F, G, and H, 

 habit drawings of successive stages ; B, D, I, J, and L, diagrammatic longisections showing 

 relation of floral parts at successive stages ; K, face view of a stage somewhat more developed 

 than /; M, face view, at stage about the age of L ; N-P, stages in development of embryo : 

 «x, vegetative axis; ^cr, floral bract; cha, cha.la.za.; cot; cotyledons; ec/, epicotyl ; emb, 

 embryo ; emb s, embryo sac ; end, endosperm ; fl p, floral primordium ; int, integuments ; 

 /■«'«/, inner integument ; «/j, nucellus ; o i«r, outer integument ; sf, ovule; « w, ovary wall ; 

 pbm, periblem ; pi, plerome ; ptf>, perianth ; sta p, staminal primordium ; sti, stigma ; stp, 

 stipule; sty, style; sus, suspensor. (Redrawn and adapted from Briosi and Tognini, Isti- 

 tuto Botanko di Pavia.') 



Styles elongate unequally, and one is always somewhat longer than 

 the other even at maturity. (Figs. io6, G, H, and 105, C) Within 

 the ovary, the remaining tissue of the primordium forms the 

 nucellus and finally a single ovule is developed which becomes 

 completely campylotropous with a curved megagametophyte. 

 (Fig. 106, /, M, N.) 



Shortly after the initiation of the carpellary wall, a second fold 

 of tissue arises at the base of the primordium, growing up and 



