NOTABLE PLANT FAMILIES 



divisions are sepals, but they are usually petal-like in appearance. 

 The three inner are petals. By a twist of the ovary what would 

 otherwise be the upper petal is made the lower. This division is 

 termed the lip ; it is frequently brightly colored or grotesquely 

 shaped, being at times deeply fringed or furrowed ; it has often 

 a spur-like appendage which secretes nectar ; it is an important 

 feature of the flower and is apparently designed to attract insects 

 for the purpose of securing their aid in the cross-fertilization 

 which is usually necessary for the perpetuation of the different 

 species of this family, all of which give evidence of great modi- 

 fication by means of insect-selection. 



In the heart of the flower is the column ; this is usually com- 

 posed of the stamen (of two in the Cypripediums'), which is con- 

 fluent with the style or thick, fleshy stigma. The two cells of 

 the anther are placed on either side of and somewhat above the 

 stigma ; these cells hold the two pollen masses. 



Darwin tells us that the flower of an orchid originally con- 

 sisted of fifteen different parts, three petals, three sepals, six 

 stamens, and three pistils. He shows traces of all these parts in 

 the modern orchid. 



XXXIX 



