THE PISTIL. 15 



80. The degree of the partitioning of a compound ovary into cells is also 

 variable. When the united edges of the carpel leaves do not turn in far, 

 and bear their ovules along the lines thus formed (placentae), on the 

 walls of the common cell, the ovules are said to be borne on parietal 

 placenta? (from L.- paries a wall). 



81. Passing now many intermediate grades, we find pistils (Figs. 41- 

 4, 5), where the infolding extends to the center or axis of the ovary, 

 making a number of distinct cells by complete partitions (called dissepi- 

 ments)', or in other words, the pistil seems to be made up by the union 

 along their sides of so many closed carpels. In these the ovules are of 

 course borne along the inner or central sutures, and they are said to be 

 on axial placenta*. 



82. Cases are found (Fig. 31), in which the partitions have entirely 

 disappeared, and the ovules are then borne upon a post or column in the 

 center of the ovary, and they are said 



to be on a free axial or central pla- 

 centa, and the ovary is plainly one- 

 celled. However, the compound 

 nature of such pistils is readily seen 

 by the number of styles or stigmas. 



83. The forms of pistils considered 

 above are closed pistils, and they 

 characterize the sub-class of Flowering 

 Plants known as Angiosperms (Greek, 



ayyfiov and ffTtepjua, enclosed seed). FIG. 31. 



The only way the pollen can reach the 



enclosed ovules is by sending out very minute tubes, which penetrate 



through the stigma and down the style to them. Another form of 



pistil is 



84. The Open Pistil. In this the carpel leaf instead of folding together 

 remains open, in the form of a scale, and bears two or more ovules on 

 the upper (inner) surface near the base. These scales grow imbricated 

 together in a close spike cone as seen in the representatives of the 

 Pine family. At the time of flowering they are divergent, and the pollen 

 is allowed to fall directly onto the exposed ovules. The scales then 

 close together and remain so until the seeds mature, when they open and 

 liberate them. 



85. This form of pistil characterizes the remaining sub-class of Flower- 

 ing Plants, viz., the Gymnosperms (Greek, yvj^ros, naked, and aTtep^a, 

 seed). 



86. We have now found, as shown in the foregoing pages, the two 

 parts pollen and ovule for the production and bringing together of 

 which all the parts of the flower fire subservient. The organs which 

 produce them stamens and pistils are called the essential organs, 

 because they are essential for the propagation of the species, and must 

 always exist either in the same or separate flowers. It remains for us to 

 consider certain 



87. Terms of More General Application to the Parts of the 

 Flower. In our type flower, shown diagrammatically in Fig. 27, 



Fig. 31. Flower of the Purslane cut through lengthwise. (From Gray.) 



