66 



DICOTYLEDONS 



those in the middle have a small yellowish, tubular corolla (ktbular 

 florets 1. 2, 3, 4), whereas those on the margin possess a corolla 

 stretched out in a long, yellow tongue {ligulate florets, L). 



Fig. 68. — Longitudinal section of tlio head of the Sunflower. 1 —4 Tiil)ulai- florets; 



1. not yet opened; 2. the pollen is pushed out of the flower tube; 3. the style 



protrudes and exposes its two-cleft stigma; 4. faded flowers. — L. Ligulato florets. 



B. Bracts. R. Common receptacle. H. Hollow part of receptacle ami stem. 



(a) Tubular florets. — The head of a Sunflower generally 

 shows florets in various stages: those in the centre may be mere 

 buds (i) ; then follow one or two circles of opened florets bearing 

 clusters of pollen at their tops (2) ; then come florets with their 

 forked styles visilde (3) ; and finally, florets, which are faded, form 

 the outer circles (4). Let us now examine one of the tubular 

 florets (fig. 69). The ovary (0.), we find, rests in a hole of the 

 cliaffy receptacle. It bears two small scaly leaves on it wliich 

 represent tlio calyx-loaves (C.). In some species of this order, as 

 for instance the Sow-thistle (Sonchus oleraceus), Lettuce {Lactnca), 

 and in Vernonia ciuerea tliese calyx-leaves crown the fruit, when 

 ripe, with a featliery ring of hairs, called pappus, l)y which tlie 

 wind carries the seed far away. The fruit of the Sunflower have 

 no such pappus. 



The corolla of the inner florets is, as already remarked, a 

 narrow tube. At its l)ase there is a ball-like enlargement, and 



