560 THE STRUCTURE OF ECONOMIC PLANTS 



is bilobed, the lobes being separated by connective tissue; and 

 each one develops two microsporangia which extend its full length. 

 The abaxial surface of the anther is papillate, while the adaxial one 

 has few hairs. No stomata are present. 



In the bicarpellate types, the carpellary primordia arise soon 

 after the differentiation of the stamens. They appear centrad to the 

 joint petal-stamen zone, and are so arranged that one carpel is 

 opposite a stamen, the other being alternate with two stamens. 

 (Fig. X94, E, F.) In hexamerous forms, the six-carpellary pri- 

 mordia are alternate with the stamens. (Fig. ^^i, C) The early 

 development of the two carpels results in the formation of conical 

 hood-like structures whose concave faces oppose each other. 

 Within the carpel primordia, there remains a definite portion of 

 the axis which consists of a more or less flat or concave disk. This 

 part of the axis begins to elongate, and enlarges to form a conical 

 structure. (Fig. 194, G.) Later, growth is initiated at the base 

 of the elongating cone; and two septa develop involving a portion 

 of the axis and forming two locules. At this time, each carpel is 

 open at the top; and its cavity is a pit bordered by the elongated 

 central portion of the axis, the ridge-like septa, and the curved 

 walls of the carpel. (Fig. 1.^^, H.) Continued growth of the 

 carpels results in the tip of each being inclined toward the central 

 portion of the axis, and finally they become so closely appressed 

 to the elongated column of the axis that the two structures are no 

 longer recognizable as distinct from each other. Further elonga- 

 tion of the terminal portions of the carpels results in the formation 

 of a long narrow style. Continued enlargement and a bowing out 

 of the basal wall of each carpel forms two locules in which the 

 central axis develops as a columnar structure from which the 

 ovules arise. (Fig. 1.^1., D, and Fig. 194, Z.) 



Although the placental structure is at this stage continuous 

 with the carpellary tissue, it is largely cauline in origin; and the 

 ovules may be regarded as arising from cauline, axile placentae 

 rather than from foliar ones. (Fig. 193, C) The epidermal cells 

 of the ovary as well as of the basal portion of the style are papillate; 

 and multicellular, glandular, and non-glandular hairs are also 

 produced. Cooper (7) observed a few large stomata in the stylar 

 epidermis, but found none in the epidermis of the ovary, agreeing 

 in this regard with Groth (n), Rosenbaum and Sando (i6), and 

 Gardner (10). Both Gardner and Cooper reported stomata on the 



