LECTURE XXVI. 



LIKE the Pine the Buttercup reproduces itself by means of seeds. 

 The seeds of the Buttercup are formed in connection with the 

 flowers. The flowers are produced at the ends of the branches of 

 the upright stem. The ends of these branches terminate in a cone- 

 shaped enlargement. This is the axis or thalamus of the flower 

 on which the specialised floral leaves are inserted. The leaves 

 belong to four different categories. 



The five or six outermost or lowest are ovate and pointed ; they 



are attached by a broad base to 

 the lower part of the cone-shaped 

 axis, where its diameter is great- 

 est. They are pale green. Each 

 is called a sepal and they form 

 together a circle, or whorl, round 

 the axis, known as the calyx. 



In Ranunculus bulbosus their 

 outer ends are bent backwards 

 along the stalk of the flower. In 

 R. repens each is boat- shaped 

 and is directed obliquely up- 

 wards. While the young flower- 

 bud is developing the sepals 



Ranunculus repens, flower, cover it over, and only when it 

 a > is approaching maturity do they 

 bend backwards and open to 

 allow the inner leaves to expand. 

 Hence it is believed that their 

 the soft tissues and immature organs of 



FIG. 80. 



longitudinal section, x 7 

 carpels; b, stamens; c, petals; d, 

 sepals; e, axis showing conducting 

 tracts ; /, ovules. 



function is to protect 

 the developing flower. 



Within and above the calyx is the corolla. It is composed of 

 the same number of petals as the calyx has sepals. The petals 

 are attached to the axis just above the sepals and they alternate 

 with the sepals. They are brilliant yellow, glossy on the upper 

 surface and dull beneath. The yellow colour is due to a pigment 



230 



