SPRING FLOWERS 123 



The parts within are best seen on stripping both the sepals 

 and petals from a flower. This leaves the stamens standing on 

 the floral receptacle around the pistil (Fig. 62). There are six 

 stamens, two of which are shorter and stand farther away from 

 the pistil, while the other four are longer and are grouped in 

 two pairs. The two shorter ones stand lower on the receptacle, 

 and are placed on either side of the flower immediately within 

 the bulged-out sepals of the inner pair. Each stamen consists of 

 a stout greenish stalk supporting the anther, the pollen sacs of 

 which at first face inwards towards the centre of the flower. 

 When examining the stamens the nectaries will be seen. The 

 green rim around the base of each short stamen is a nectar- 

 secreting gland, and a smaller nectary is present just below each 

 pair of long stamens. The nectar secreted by these glands 

 accumulates in the bag-like bases of the two inner sepals. 



The pistil, which is borne on the summit of the receptacle 

 and stands in the centre of the flower, presents difficulties to 

 the observer on account of the small size of the parts. It is 

 differentiated into a green ovary surmounted by a stigma which 

 is slightly two-lobed. It is composed of two carpels joined 

 together edge to edge, and the cavity of the ovary is divided 

 into two by a longitudinal partition. In each half there are 

 two rows of ovules lying against the partition (Fig. 62, B). [The 

 structure of the pistil in the Charlock, where it can be more 

 easily studied, should be compared.] 



The flowers are visited by numerous insects, which come 

 in search of the nectar concealed at the base of the flower. In 

 sucking this they will place their heads between the stamens 

 and the stigma, and on going to another flower may touch its 

 stigma with the pollen-covered surface of their heads and so 

 effect cross-pollination. The risk of direct self-pollination by 

 the pollen from the anthers of the longer stamens falling on 

 the stigma is lessened by the anthers making a half -turn outwards 

 when the flower opens. 



For some reason or another the flowers often do not set fruit. 

 The construction of the fruit and its mode of opening, should 

 specimens be found, will be understood from the description 

 given in the following chapter of the fruit of the Charlock. 



