372 THE HIGHER DICOTYLEDONS. 



How broad are the heads ? Note the shape of the expanded 

 top of the head (slice it down longitudinally) and the struc- 

 ture of the involucre (number of bracts ? in how many circles ? 

 shape and colour of bracts ?). 



You will notice that the outer flowers, forming a single 

 series, resemble those of the Dandelion in having a strap- 

 like outgrowth from the mouth of the corolla, while all the 

 inner flowers have a tubular corolla ; the strap-like (ligulate) 

 flowers are often called the ray-flowers, the small tubular 

 ones the disc-flowers. Compare a ray-flower of Daisy with 

 a Dandelion flower : note the shape of the strap, the narrow 

 but short stigmatic arms, the absence of stamens. In a 

 disc-flower note the regular tubular corolla, with five (some- 



INVOLUCRE 



Fig. 153. Vertical Section of Capitulum. 



times only four) equal lobes round its edge, the thick short 

 stigmatic arms, the presence of stamens. The ray-flowers 

 thus differ from the disc-flowers in having no stamens, as 

 well as in the shape of the corolla. In what respect do all 

 the flowers differ from those of Dandelion ? 



Note the closing of the head at night and in bad weather. 

 On a bright day the straps of the ray-flowers spread out 

 horizontally, at night they move inwards and meet at the 

 tops so as to cover and protect the young central flowers. 



Is it possible to make the head close in the daytime ? 

 Cover a plant with a flower-pot or box, excluding all light by 

 sprinkling soil round the edges where the pot or box rests on 

 the ground. Keep a Daisy in darkness for two or three days, 

 then bring it to the light, or remove the pot or box covering 



