STRUCTURE OF FLOWERS 7 



extinct, is the next step, the labellum being formed into a 

 pouch with infolded side lobes. The column has a promi- 

 nent staminode with two fertile anthers below it, one on 

 each side of the column and behind the stigmatic plate. 

 The upper sepal is frequently the showiest feature in the 

 flower ; the lower sepals are joined and arranged behind 

 the lip, whilst the petals extend on each side and vary 

 much in form. 



In gardens, the whole of the genus is known as Cypri- 

 pedium, although the South American species (Seleni- 

 pedium), having a three-celled ovary, differ widely from the 

 one-celled East Indian and Malayan species, and other sec- 

 tions have such marked and consistent botanical differences 

 as to warrant the botanist in separating them under dif- 

 ferent sub-generic names. The third section of Orchidae, 

 the largest family of the Monocotyledons, forms the chief 

 class of Orchids as they are known in gardens. In this 

 class the stamens and style unite into a column, and at the 

 top of the column the pollen masses are situated ; these are 

 covered by the anther-cap, and in a cavity is the stigma 

 with its viscid surface to receive the pollen grains. 



So diverse and intricate are the forms of the flowers, and 

 especially labellums, that there is little doubt that insect 

 aid is necessary in their natural habitats to bring about 

 pollination. It has been proved by the operations carried 

 out in cross-fertilisation in gardens that no class of plants 

 can be so readily crossed under artificial conditions. It is 

 not necessary here to go further into structural details, as 

 the peculiarities of each section will be remarked on under 

 their different headings. But it may be said that in what 

 are called abnormal flowers, which have perfect stamens 



