340 



THE HIGHER DICOTYLEDONS. 



are joined at the base to a short outgrowth from the stem. 

 Note the bract on the flower- stalk ; the inflated and five- 

 angled calyx with five narrow pointed lobes ; the corolla, 

 consisting of a tube and a flat broad upper portion, the limb 

 with five notched lobes. The corolla-lobes are pale yellow, 

 but round the mouth of the tube there is an orange-coloured 

 ring with thickened folds ; this ring is sometimes represented 

 by five patches (one to each lobe) darker in colour than the 

 rest of the expanded limb. The limb serves as a platform on 

 which the insect- visitors (chiefly bees) stand, and the orange 

 ring acts as a honey-guide, enabling the insect to reach the 

 centre of the flower more quickly and certainly. 



Note the five stamens, which are, in some flowers, at the 

 mouth of the tube, and can then be seen to stand opposite 

 to the lobes; it is characteristic of 

 & the Primrose family (Primulaceae) 



to have the stamens equal in number 

 to the corolla-lobes and opposite to 

 (not alternate with) the lobes. Open 

 up the corolla-tube of a flower of 

 this kind (" thrum-eyed ") : the fila- 

 ments of the stamens are very short 

 and are inserted near the mouth of 

 the tube, while the stigma is about 

 half-way up the tube. Note the 

 structure of the ovary : it is one- 

 chambered, and the numerous ovules 

 are attached to a rod (placenta), 

 which projects from the floor of the 

 chamber upwards but does not reach 

 the roof, so that the ovary-wall may be removed leaving the 

 ovules attached to the free central placenta. 



Now examine other flowers on (1) the same plant which 

 bears the kind of flower just described, (2) other plants. 

 Do you find that (1) all the flowers on the first plant are 

 " thrum-eyed " (short- sty led), (2) some plants have a different 

 type of flower in which the stigma is at the mouth of the tube, 

 while the stamens are inserted half-way up ? this is the " pin- 

 eyed " or long-styled form. The two kinds of flower appear 

 to be always on distinct plants, and the plant apparently 

 produces flowers of the same kind year after year. So that 



Fig. 138. Floral Diagram of 

 Primrose. 





