118 THE PEA. 



The _F'2ower is nodding, 5-parted, and irregular after a 

 fashion termed papilionaceous (butterfly-shaped). There are 

 5 sepals, united at the base and free above. Of the 5 petals 

 (1 ) the upper and odd one is the largest, and in the bud 

 covers all the rest. It is called the banner or vexillum. 

 The others are in pairs ; the 2 lowest being the keel petals 

 (carince) ; the 2 intermediate, the wings (aim).* Of the 10 

 stamens (2), 9 are united by their filaments, while the 10th 

 is separate and free, a condition termed diadelphous, that is, 

 in 2 sets. The pistil is one only, and that (3) 

 a simple carpel with one style and stigma. The 

 style is bent at a right angle, and flattened as if 

 laterally, with a groove on the back and a bearded 

 line in front next the free stamen, f 



The Fruit is a legume. It is a dry pod, 

 oblique in form, one-celled, 2-valved, opening at 

 both its edges (sutures) and having the seeds in 

 one row along the front suture not along both 

 as in a silique (p. 101). Much is learned by a 

 careful study of the legume. Open it at the 

 7, a legume, front suture. The two valves still conjoined at 

 the back will represent a leaf, with seeds like buds developed 



horizontally, describing in an hour or two a complete circuit, like the free end of the 

 twining stem or branch of the Morning Glory (p. 186). When at length the tendril, 

 with the hook at its extremity, touches a twig or other object, it immediately twines 

 about it, while at the same time in its middle portions it coils up on itself, as if by 

 shortening its own length to draw the plant closer to its support. The mechanical 

 difficulty of coiling up while fixed at both ends is overcome by its turning in opposite 

 directions, causing a sharp angle where its course is reversed. This is best seen in 

 the Gourd Tribe and the Grape-vine. After its hold is thus secured it grows strong 

 and tough ; but if it fails to reach its object it soon droops, coils up, and perishes. 



* In the Pea tribe the banner is brightly colored so as to justify the name, since 

 when expanded it cannot fail to attract insects. The lower petals are frequently 

 joined together in one piece, forming a kind of doorstep on which the insects may 

 readily alight. On their attempting to enter the throat of the flower, by springing 

 open the alae, the stamens beneath are liberated and are dashed with some force 

 against the insect's body, so as to cover it with pollen. 



t In the Sweet Pea, cf the genus Lathyrus, the style is flattened on the back and 

 in front ; and this circumstance alone separates these two genera. 



