THE FLOWER. 



47 



X220. 



is polype talous ; very irregular and resembles more or less 



remotely a butterfly, 



and for this reason 



it has received the 



name Papilionaceous 



{Jjixt. papilio, butter- 

 fly) ; the upper and 



larger petal is called 



the banner, or vex- 



iUum (Fig. 107, V) ; 



the two side petals 



are called the wings, 



or ala (Fig. 107, a) ; 



and the two anterior 



ones, generally cohering slightly (and enclosing the stamens 



and pistil), are called the heel (Fig. 107, k). The flowei-s 



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. crua:, 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 

 f'^/Zf// '^'y^^\ 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 

 is two-spurred. All the petals of 



Fig. 106. A head of flowers of Heliopsis : i», involucre ; d.Jl^ disk-flowers ; Itff, 

 ray-flowers; ch, chaff; acli, achemia. Fig. 107. A Papilionaceous flower of Pea: 

 V, vexilKim ; a, wings ; /•, keel. Fig. 103. A Cruciform corolla. 



