522 BOTANY OF THE LIVING PLANT 



layer of the tissue of the very numerous carpels (Fig. 430) ; in the Cherry 

 and Plum from tlie corresponding tissue of the single carpel. 



ORDER; LEGUMINAI.es. 



This is one of the largest and most important families of Plants, and it is 

 cosmopolitan. It is characterised by its gynoecium, which consists of a single 

 carpel, ripening as a Legume, or Pod, as in the Pea. It is divided into three 

 Families : the Mimoseae, which are the most primitive, having fiowers of 

 radial symmetry, as in Mimosa and Acacia ; the Caesalpineae, which have 

 zygomorphic fiowers, as in the Tamarind, or Cassia ; and the Papilionaceae, 

 or Pea-flowers. The last of these only are represented in the British Flora. 

 The Order yields most varied products of importance : food-stuffs, timbers, 

 drugs, and dyes, etc. 



Family : Papilionaceae. Examples .- Trefoil, Pea. 



(30) The Bird's Foot Trefoil [Lotus corniculatns , L.) forms many straggling 

 branches from a central root-stock. The leaves have green " stipules " which 

 are really basal pinnae, and three distal lobes, hence its name. The flowering 

 branches are leafless, but bear distally a leafy bract and a radiating group of 

 flowers. Each flower is strongly zygomorphic, its plane of symmetry being 

 vertical and median, as it is in all of the Papihonaceae (Fig. 431). It is com- 

 posed thus : 



Calyx, sepals 5, gamosepalous, inferior, the odd sepal being anterior. The 

 calyx-tube gives mechanical support to the internal parts, and is shghtly 

 widened in a perigyuous manner. 



Corolla, petals 5, polypetalous, inserted separately on the slightly widened 

 receptacle, i.e. perigynous. The petals alternate with the sepals. The 

 posterior petal is the large vexillum, or standard ; the two lateral are tlie 

 alae or wings, which invest the anterior carina, or keel. The latter is formed 

 from two obUquely anterior petals, inserted by separate stalks, but fused 

 distally, so as to enclose the stamens and carpel. 



Androecium, stamens 10, perigynous : nine are united by their stalks into 

 a tube ; the tenth, which is posterior, is separate to its base. The anthers are 

 completely enclosed in the carina. 



Gynoecium, carpel i, apocarpous, superior. It is a pod, containing numerous 

 ovules, with placentation on the posterior margins. The style is longer than 

 the stamens, and bears a capitate stigma. The pod is almost surrounded by 

 the united filaments, but access to the honey-secretion, which is on the enlarged 

 receptacle round its base, is gained through the slits right and left of the 

 separate stamen. The fruit when ripe is a dry pod, sphtting longitudinally 

 into halves. 



Pollination. The mechanism of the flower is elaborate, and secures cross- 

 pollination notwithstanding the close relation of anthers and stigma, which 

 are both enclosed in the funnel-Uke carina. For the stigma is not receptive 

 until it has been rubbed, and remains infertile till the insect-visitors, which 

 are bees, arrive. Searching for nectar, and guided by the converging red 

 lines on the standard, the bee alights on the projecting wings ; its weight is 



