58x THE STRUCTURE OF ECONOMIC PLANTS 



staminate flowers are located near the center of the vine and are 

 borne on slender peduncles; while the pistillate flowers are borne 

 on short ridged stalks, distal to the staminate ones. In the bushy 

 types, the pistillate flowers occur near the base of the plant. The 

 character of the peduncle is sufficiently distinct in the three species 

 to be used as a diagnostic character. In C. Pepo, the fruit stalk is 

 deeply furrowed and five- to eight-ridged; in C. moschata, it is 

 five-ridged and enlarged next to the fruit, and in C. maxima, the 

 peduncle is cylindrical or claviform but never prominently ridged. 



The Carpellate Flower. — The carpellate flowers are epigy- 

 nous. The calyx tube is terminated by five slender awl-shaped 

 lobes, and the companulate corolla is also deeply five-lobed, the 

 lobes being recurved at the tips. (Fig. 304, A, 5.) The pistil 

 consists of three carpels which form a three-loculed ovary, and the 

 thick, short style is terminated by three bilobed or divided papil- 

 late stigmas. Occasionally, the pistil may consist of four or five 

 carpels with a resultant four- or five-celled ovary. The stamens 

 are rudimentary, three staminodia being commonly present; and a 

 ring-like nectary is located between the base of the perianth tube 

 and the style. (Fig. 305, A.') 



The development of the pistillate flower has been investigated 

 by Kirkwood (ix) for several genera of Cucurbitaceae; and by 

 Judson (xi) for Cucumis, as well as by several of the earlier mor- 

 phologists, including Payer (31) and Goebel (13). These accounts 

 are in general agreement, except for diff'erences in the interpretation 

 of the development of the ovary and the character of its placentation. 



The floral axis first develops as a rounded protuberance which 

 elongates. The apex then becomes flattened, and a slight terminal 

 depression develops so that the surface is somewhat concave. The 

 primordia of the floral parts arise from this surface in acropetal 

 succession: sepals, petals, staminodia, and carpels. Because of 

 diff"erential growth at five points on the margin, outgrowths arise 

 which are the primordia of the sepal lobes. Growth of these 

 lobes, and of the underlying tissue at the outer margin of the 

 receptacle, results in an elevation of the outer border of the re- 

 ceptacle; and the inward curvature of the densely pubescent lobes 

 tends to cover the tip of the floral axis. At this time, the cen- 

 tral portion of the stem apex grows slowly; and the more rapid 

 growth of the outer portion forms a cup-shaped receptacle which 

 surrounds it. 



