THE BROAD BEAN PLANT. 



11 



end of the flower-stalk, to which all the parts of the flowers are 

 attached). In each wing note the narrow stalk, and the broad 

 oval portion which has a large blackish spot. Gently pull each wing 

 outwards, and note that it clings to the outer surface of the keel : can 

 it be pulled off without tearing anything ? Note the way in which the 

 wing on each side is locked with the keel ; at this place the wing and 

 the keel show a series of folds, the corrugated surfaces fitting together. 

 Remove and sketch one of the wings, both from the inner side and 

 the outer side. In removing the 

 standard and the wings, note 

 that these pieces (petals) alter- 

 nate in position with the calyx- 

 lobes, i.e. the insertion of each 

 of these three petals is just in- 

 side the space between two of 

 the calyx-lobes. Now examine 

 the keel, and note that it is 

 carried on two separate stalks ; 

 detach these at their bases and 

 pull them apart, when the keel 

 will split along its sharp lower 

 edge into two pieces. The 

 corolla, then, consists in reality 

 of five petals, the two lowest 

 being attached to each other to 

 form the keel, and the five petals 

 alternate in position with the five sepals (calyx-lobes). 



Pig. 3. Stamens and Pistil of Broad Bean. 



28. The Stamens (Fig. 3). On opening up the keel you will see 

 a number of small oval bodies (anthers), each carried at the end of a 

 thin stalk (filament). How many anthers are there ? If you see any 

 stalks bare at the end, try another flower (a young unopened flower is 

 best). Trace the stalks down, and notice that most of them are joined 

 below to a thin colourless plate which is folded longitudinally. Does 

 this folded plate form a complete tube or is it open ? Where is the 

 opening, and how is it covered over ? Are any of the filaments free 

 from the folded plate ? Each anther, with its filament, constitutes a 

 stamen, but only the uppermost stamen is free right down to the 

 flower-axis ; the others arise from the " stamen- trough." The upper 

 parts of all the stamens bend sharply upwards, to suit the shape of 

 the keel, in which they are enclosed ; there is a narrow opening along 

 the upper side of the keel, above the free stamen. 



Examine an anther with the lens, noting the two lobes divided by 

 a longitudinal groove, and each showing a less marked groove ; the 

 anther consists of four pollen-sacs lying side by side. This can only be 

 seen in a young flower ; in an older one the anther will have opened 

 by two slits, one at each side, allowing the yellow dust-like pollen to 

 escape. Sketch the ten stamens, with the " stamen- trough" as seen 

 from the side ; then cut round the base of the trough, remove it, and 

 sketch it spread out. 



