1630 A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 1489. — Ranunculus acris. Field Buttercup. 



exposed. Only large, nectar-collecting insects come into contact with the 

 stigmas, effecting both cross- and self-pollination with equal ease. 



RHOEADALES 



The Rhoeadales are Archichlamydeae in which the plants are mostly 

 herbaceous, with scattered, entire or more or less divided alternate leaves 

 without stipules. The flowers are cyclic, hypogynous or rarely perigynous 

 and hermaphrodite, with free sepals, petals and stamens. They are usually 

 actinomorphic, more rarely zygomorphic. The stamens may be definite or 

 indefinite in number and are occasionally united into two bundles. The 

 carpels are united into an ovary which may be one-chambered, with 

 numerous ovules on parietal placentas, or the ovary may be bilocular as a 

 result of the development of a septum between the placentas. This latter 

 structure is termed a false septum because it is incomplete and is not 

 produced as an ingrowth of the ventral edges of the carpels but is a new 

 structure arising late in the development of the ovary. The stigmas instead 

 of arising on the median plane of each carpel are often placed immediately 

 above the placentas, when they are said to be commissural. The seeds are 

 usually small, often curved, generally with a well-developed endosperm 

 and small embryos. 



The species are found mainly in north temperate regions. Included in 

 this order are the Papaveraceae and Cruciferae which we shall consider in 

 detail subsequently, and also the Capparidaceae and Resedaceae. 



The Capparidaceae, which are separated by Hutchinson as a distinct 

 order, are either herbaceous or woody plants mainly occurring in the tropics. 

 The chief feature which separates them from the rest of the Rhoeadales is 

 the absence, or at least very scanty development, of endosperm. A few 

 are cultivated in gardens, while the flower buds of Capparis spinosa 



