EARLY SUMMER FLOWERS 211 



formed of two carpels, and consists of a pale green, cylindrical 

 ovary clothed with downwardly pointing hairs, an ill-defined 

 style, and a stigma composed of two yellowish lobes standing 

 front and back in the flower. The structure of the ovary will 

 be best considered along with that of the fruit. 



The flowers of the Charlock are conspicuous, not merely on 

 account of their individual size, but by their aggregation in the 

 inflorescence. They are visited by numerous insects which come 

 partly to collect or feed off the pollen, but also in search of nectar. 

 This is secreted in abundance by the nectaries, which are very 

 easily seen in a flower from which the calyx and corolla have been 

 removed. One large green nectary stands just within the in- 

 sertion of each short stamen, while a smaller gland is situated to 

 the outside of each pair of long stamens. Owing to the way in 

 which the sepals diverge the honey could be reached from the 

 outside of the flower, but insects, as a rule, approach in the more 

 usual way, and, alighting on the petals, pass their tongues down 

 the centre of the flower. All the anthers at first face inwards 

 towards the centre of the flower, and those of the two short 

 stamens remain in this position. Since they stand at a lower 

 level than the stigma, there is little likelihood of the pollen 

 effecting self-pollination. The anthers of the two pairs of long 

 stamens are situated at a slightly higher level than the stigma. 

 As the flower opens they make a more or less complete half- 

 turn, and so come to face outwards. An insect sucking the 

 honey at the base of the short stamens will have one side of its 

 head against the stigma while the other is being dusted with 

 pollen. When getting honey from the nectary at the base of 

 the long stamens it will be dusted with pollen from their anthers, 

 but will not touch the stigma. Insects passing from flower to 

 flower will thus effect cross-pollination. Should this not take 

 place, after the flower has been open for some days the anthers of 

 the longer stamens bend backwards, and the stigma as it grows 

 up comes in contact with them and is self -pollinated. 



The fruit (Fig. 95) is simply the greatly enlarged pistil after 

 the sepals, petals, and stamens have fallen away. It is a long, 

 green, pod-like structure with a flattened beak, at the summit of 

 which is the remains of the stigma. There are no seeds in the beak- 



