THE FLOWER. 



47 



is polypetalous ; very irregular and resembles more or less 



remotely a butterfly, 



and for this reason 



it has received the 



name Papilionaceous 



(ILat. papilio, butter- 

 fly) ; the upper and 



larger petal is called 



the banner, or vex- 



illum (Fig. 10.7, v) ; 



the two side petals 



are called the wings, 



or alcB (Fig. 107, a) ; 



and the two anterior ^°^ 



ones, generally cohering slightly (and enclosing the stamens 



and pistil), are called the keel (Fig. 107, k). The flowers 



of the Cress, Mustard, Cabbage, etc., have four petals, 



arranged two and two opposite, somewhat like a cross, and 



they are said to be cruciform (Lat. crux, cross ; Fig. 108). 

 58. A conspicuous irregularity in the flower is caused by 



the production of appendages of various kinds. One petal 

 in the Violet is 

 prolonged so as to 

 form a spur ; this 

 organ is tubular, 

 and generally con- 

 tains Nectar, or los 

 sweet substance secreted by the 

 flower. One species of Dicentra 

 1"'' is two-spurred. All the petals of 



Fig. 106. A head of flowers of Heliopsis : in, involucre ; d.Jl, disk-flowers ; /zj-, 

 ray-flowers; c/i, chaff"; ac/t, achemia. Fig. 107. A Papilionaceous flower of Pea: 

 V, vexillum ; a, wings ; i, keel. Fig. 103. A Cruciform corolla. . 



