10 



THE BROAD BEAN PLANT. 



25. The Flowers of the Broad Bean are arranged in 

 small clusters, each cluster arising in the axil of a leaf, and 

 each flower is attached by a short stalk to the axis of the 

 cluster, which occupies the same position on the shoot as an 

 ordinary branch. The cluster or flower-bearing branch is 

 called an inflorescence. Turn down or pull off the leaf just 

 below an inflorescence, and examine the latter closely. This 

 special kind of inflorescence, with the individual flowers 

 stalked and spaced out on the axis, is called a raceme ; the 

 youngest flowers are nearest the top. 



If Broad Bean flowers are not available, use those of Sweet Pea, or 

 Gorse, or some other plant of the Bean Family. 



In dissecting flowers use a sharp penknife (a pair of fine scissors 

 will also be useful), a pair of forceps for seizing the parts of the flower, 

 and a lens. 



Note the parts of a single flower (Figs. 2, 3), starting from the 

 outside : 



26. The Calyx, a greenish or colourless cup, with its free edge pro- 

 duced into five pointed lobes. Note the veins which start from the 

 bottom of the cup, one running up the middle of each lobe, others 

 between the lobes. 



27. The Corolla (Fig. 2), consisting apparently of four pieces, a large 

 upper piece (standard), two smaller side pieces (wings), and a lower 



boat-shaped piece (keel). 

 Note the way in which 

 the standard is folded 

 below over the wings, 

 which in turn enfold the 

 keel. The standard is 

 on the upper (posterior) 

 side of the flower, i.e. 

 the side towards the axis 

 of the inflorescence ; note 

 the position of each of 

 the calyx-lobes with refe- 

 rence to the axis, the odd 

 one being the lowest. 



Open the calyx by 

 cutting or tearing it be- 

 tween the two upper 

 lobes, to see the exact 

 shape and position of each of the four parts of the corolla. Remove 

 the standard and sketch it (front surface and side view) ; note its 

 broad upper part, marked by coloured streaks, and the narrow lower 

 part by which it is attached to the receptacle (i.e. the expanded upper 



WING PETAL 



KEEL 

 STANDARD 



Fig. 2. Corolla of Broad Bean. 



