146 



PARTICULAR FORMS OF FLOWERS 



246. Flowers of alfalfa, 

 enlarged. 



247. 

 Cassia flower, 

 showing the 

 separate 

 keel petals. 



answer in all ways to this description. The term perianth 

 is used in other plants than the Liliacese. 



296. Papilionaceous Flowers. — In the pea and bean 

 tribes the flower has a special form 

 (Figs. 245, 246). The calyx is a shal- 

 low 5-toothed tube. The corolla is 

 composed of four pieces, — the large 



expanded part at the back, 

 known as the standard or 

 banner; the two hooded side 

 pieces, known as the wings; 

 the single boat-shaped part 

 beneath the wings, known as 

 the keel. The keel is sup- 

 posed to represent two united 



petals, since the calyx and stamens are in 5's or multiples 



of 5; moreover, it is of two distinct parts in cassia (Fig. 



247) and some other plants of the pea family. Flowers of 



the pea shape are papilionaceous 



(Latin papilio, a butterfly). 



297. Flowers of the pea and its 

 kind have a peculiar arrangement 

 of stamens. The stamens are 10, 

 of which 9 are united into a tube 

 which incloses the pistil. The tenth 

 stamen lies on the upper edge of the 

 pistil. The remains of these sta- 

 mens are seen in Fig. 206. The sta- 

 mens are said to be diadelphous ("in 

 two brotherhoods") when united into 

 two groups as in this case. Stamens 

 in one group would be called mona- 

 delphous, and this arrangement 24S - Common mallow, a trailing 



CT plant to which the circle of 



occurs in some members of the fruits, a, gives the names 



T . » ., "cheeses" and "shirt button 



LeguminosaB or pea family. plant." 



