MORPHOLOGY OF ANGIOSPERMS. 123 



or carpels occupy the terminal portion of the branch while the 

 stamens and floral leaves occur in circles or whorls below. 



Pistil. — There may be only pne carpel present in a flower 

 or there may be more. In the latter case the carpels may remain 

 distinct or they may be united, but whatever the number or the 

 degree of union, it is the carpel or carpels which constitute the 

 closed structure known as the pistil. The pistil is usually differ- 

 entiated into three quite distinct regions : ( i ) A lower bulbous 

 portion which contains the ovules, known as the ovary; (2) a 

 neck-like portion known as the style; and (3) at the top of 

 the style a specialized portion which receives the pollen, known 

 as the STIGMA (Figs. 83 and 85). When the pistil is made up 

 of a single carpel it is said to be simple, and when composed 

 of more than one carpel it is called compound. 



The carpels in the compound pistil appear to be united in 

 different ways. Sometimes they appear to have coalesced or 

 grown together at the margins, thus fonning an ovary with but 

 one chamber or compartment (Fig. 84, B). In other cases the 

 carpels appear as though they were incurved or folded together at 

 the margins along the line of union, thus forming septa or walls 

 which divide the inner cavity into several compartments or 

 locules (Fig. 84, A, C). 



When the carpels are not united but remain separate, there 

 are as many pistils as carpels, as in the flowers of buttercup ( Fig. 

 84, D). Thus a unilocular ovary may belong to a simple or com- 

 pound pistil. 



Gyn^cium. — The aggregate of pistils in a flower constitutes 

 the gynsecium. If the gynsecium is made up of a number of simple 

 pistils, as in the flower of buttercup (Fig. 84, D), it is said to be 

 APOCARPOUS. But if the carpels are united into one structure, then 

 the gynsecium is said to be syncarpous, as in the orange flower, 

 which is in reality equivalent to a compound pistil. Inasmuch as 

 the styles and stigmas are frequently not united the expression 

 compound ovary is usually employed. According as the gynse- 

 cium consists of one, two, three or many carpels, it is said to be 

 monocarpellary, dicarpellary, tricarpellary or polycarpellary. 



The pistil of the flower of the pea is simple and has an elongated 

 ovary, and upon dissecting the ovary and also making a trans- 



