640 BOTANY OF THE LIVING PLANT 



Gynoecium, carpels 4, syncarpous, superior, style elongated, with capitate 

 stigma. Ovary with 4 loculi, ovules minute, numerous, on an enlarged axile 

 placenta. Honey-disc round the base of the hairy ovary. 



Fruit, a loculicidal capsule, from which the minute seeds are shaken by wind. 



Pollination is by bees, which hang on to the pendent flowers. The bee first 

 touches the sticky stigma, depositing pollen it may have brought from another 

 flower ; then inserting the proboscis, it collides with the spurred stamens, 

 shaking out a shower of dry pollen. Thus there is a high probability of cross- 

 pollination, though self-pollination is possible by some falling upon the stigma 

 of the same flower. The gamopetalous corolla with narrow mouth, and the 

 spurred stamens exclude small thieving insects. 



(34) Compare the Bilberry (V actinium Myrtillus, L.), in which the floral 

 structure is essentially the same, but the ovary is here inferior. In this genus, 

 and in the Ericaceae generally, there is frequent meristic variation, the flowers 

 being either tetra-merous or penta-merous. 



ORDER : PRIMULALES. 

 Family : Primulaceae. Example : Common Primrose. 



(35) The Primrose {Primula vulgaris, Huds.) is a perennial with its stock 

 covered with old leaf-bases, and ending in a rosette of leaves of the current 

 year. The flowers are borne singly in the axils of bracts, which succeed the 

 foliage leaves. There are two types of flower which are borne on distinct 

 plants : " pin-eyed," with the stigma occupying the centre of the flower, and 

 " thrum-eyed," where its place is taken by five anthers. It will be seen, 

 however, that in number and arrangement of the parts both are alike : the 

 difference is one of proportion of development of the parts (Fig. 492). For 

 convenience a " pin-eyed " flower may be taken ; it consists of : 



Calyx, sepals 5, gamosepalous, inferior, forming a tube supporting the corolla. 

 The odd sepal is posterior. 



Corolla, petals 5, gamopetalous, inferior, alternating with the sepals, and 

 forming a long narrow tube below, with five lobes diverging at right angles 



from it. 



Androecium, stamens 5, epipetalous, inserted with very short filaments 

 half-way up the tube of the corolla, and opening inwards (Fig. 492, 11.). 

 Note that the stamens are opposite the petals (anti-petalous) . 



Gynoecium, carpels 5, syncarpous, superior ; style elongated so as to carry 

 the pin-headed stigma to the throat of the corolla. Ovary turgid, unilocular ; 

 ovules numerous, placentation axile. 



Fruit, a capsule opening distally by ten teeth, which become reflexed. 

 The number five of the carpels is inferred from comparison with other flowers, 

 and from the parts of the Primrose itself. The ten teeth of the fruit support this 

 view. The anti-petalous position of the stamens, and the number (n), instead 

 of (n + n), suggests that five sepaline stamens have disappeared : this conclusion 

 is supported by the fact that in Samolus, Lysimachia, etc., five small 

 staminodes are present in the place where the missing stamens should be. 

 The family shows meristic variation, the whorls varying in number of parts 

 from four to nine. Trientalis and Lysimachia are specially variable. 



