618 



WEED FLORA OF IOWA 



FiQ. 479. Corn-poppy with a shield-shaped stigma capping the ovary. 

 (After Thomfi.) 



If we cut a cross section of the ovary of the May apple, we find 

 within, a cavity beapng on one side a projection to which are at- 

 tached the small, somewhat globular bodies or ovules. This cavity 



Fio. 480. Pistil of Thistle. 

 (After Thome.) 



within the ovule is usually called a cell by manuals, but a better 

 term is loeulus, since the term "cell" is universally used to desig- 

 nate the unit of tissues. The thickened portion to which the ovules 

 are attached is the placenta. 



The pistil of the May apple is a simple pistil and according to 

 the older views concerning the pistil, it is a carpel. The older 

 view was, that the carpel is a modified leaf. If one will imagine 

 a leaf folded and the margins joined so as to enclose a loeulus and 

 then the outer part modified so as to form a style and stigma, the 

 (!onception of a carpel will be clear. An examination of the pistil 

 of oxalis will reveal five styles and stigmas, and one ovary with 



