178 FLOWERS 



organs grow are the nodes and the spaces between the circles 

 are the internodes. 



The internodes may lengthen and separate any of the 

 circles. When the elongation is between the calyx and 

 corolla, it is an anthophore; when between corolla and andrce- 

 cium, it is a gonophore; when between andrcecium and 

 gyncecium, it is a gynophore; and when the elongation of the 

 torus elevates the carpels, as in anise and other Umbelliferse, 

 it is a carpophore. 



The Calyx. The sepals, which make up the calyx, are 

 extremely variable in size, form, color and surface in different 

 species of plants. In the typical flower the sepals are green 

 and leaflike in appearance; in the yellow field lily, erythro- 

 nium and many other species the sepals are similar to the 

 petals and can be distinguished only by their position. When 

 the sepals are not united the calyx is chorisepalous; when 

 they are united it is gamosepalous. A gamosepalous calyx 

 may and usually does assume many curious forms which will 

 be explained in detail under forms of gamopetalous corollas. 



Duration of the Calyx. The calyx is caducous if it falls 

 off shortly after the flower opens, as in bloodroot; it is decidu- 

 ous when it falls after fertilization, as in most flowers; it is 

 persistent when it remains and surrounds the fruit, as in 

 Indian tobacco and ground cherry. 



The Corolla. The corolla which consists of petals, is the 

 second circle of the flower when four are present and is 

 usually the most conspicuous part of the flower. When 

 the petals are not united the corolla is choripetalous, when 

 they are united it is gamopetalous. Petals are usually bril- 

 liantly colored and sweet scented, because of the presence 

 of volatile secretion products. The corolla also secretes 

 nectar and, when gamopetalous, is extremely variable in 

 form. When a flower has no petals it is apetalous. 



