472 



COMPOSITE 



structure, the tip of which is notched (3, Fig. 147)- A corolla 

 of this form is described as ligulate. The rest of the parts are 

 similar to those of the disk florets. 



Both the ray florets and the disk florets are sessile upon a 

 short, thick button-shaped axis which is designated the receptacle 

 of the capitulum, an unfortunate term likely to be confused with 

 the receptacle of a flower, with which however it has nothing 

 to do. 



A large number of genera, the species of which have capitula 

 composed of tubular florets only, or of tubular florets and an 

 outer whorl of ligulate florets, are united to form a division of 

 the Compositse known as the TubulifloR-«. Plants belonging 

 to this series have watery juice in their stems and leaves. 



Another group of genera, termed the Liguliflor^, is formed 

 of those species whose capitula bear only ligulate flowers. Plants 



belonging to the Liguliflorae, 

 of which the dandelion and 

 sow-thistle are examples, 

 have milky juice (latex) in 

 their stem and leaves. 



A single flower from the 

 capitulum of the dandelion 

 is seen in Fig. 148. It is 

 bisexual with a ligulate 

 corolla formed of five petals 

 shown by the five notches 

 at its tip. The calyx is 

 composed of silky hairs 

 which encircle the upper 

 part of the ovary. This ring 

 of hairs grows most rapidly 

 after fertilisation of the 

 flowers when the fruit is ripening: it is termed tht pappus, and 

 acts as a parachute for the distribution of the fruit by the wind. 



Fig. 148.— I. Single Floret of Dandelion {Tar- 

 axacum officinale Web ). o Inferior ovary ; 

 fi pappus (calyx) ; a anthers of stamens ; ytheir 

 Ataments ; « style and divided stigma ; c ligu- 

 late corolla. 



2. Fruit (cypsela) developed from i. s Stalk 

 of the pappus j^. 



3. Fruit (cypsela) of Groundsel (Seiucio 

 vulgaris L.) with sessile pappus. 



