COMPOSITE 



231 



are united in a tube. The flower-head is surrounded 

 by an involucre, consisting of more or less numerous 

 bracts. It serves in some cases to support the florets ; 

 if these are taken away from the flower-head, say of a 

 Thistle or a Centaurea, the involucre contracts and 

 closes together, showing how closely it compresses the 

 florets. In other cases, as in Carlina, it contributes 

 much to the conspicuousness of the flower-head. The 

 calyx is absent, or represented either by a narrow ring 

 or by a pappus, often of long feathery hairs. The 

 corolla is tubular, with a four- or five-toothed border. The 

 ovary is inferior, with a filiform style, divided at the 

 top into two short branches bearing the stigmas. Honey 

 is secreted at the base of the style. Hildebrand has 

 pointed out that while the small disk flowers fade, as 

 usual, when fertilised, the ray flowers remain fresh until 

 all the florets of the disk are impregnated, clearly show- 

 ing their relation to the flower-head as a whole. This 

 is the most extensive and widely distributed family of 

 plants. There are over 10,000 

 known species. We have in 

 Britain no less than 40 genera. 

 It is hardly necessary to say 

 that what we call a " flower " 

 in, say, a Daisy is really a com- 

 bination of many small flowers 

 or florets. In many the heads 

 close up in wet weather, thus 

 protecting the pollen and stigma, 

 as, for instance, in Hieracium, 

 Bellis, and Carlina. It is said 

 that wdien once closed, even if 

 the sun comes out again they will 

 not reopen till the next morning. 

 We may take Chrysanthemum 

 Parthenium (Fever - few) (Fig. 

 149) as a type of the order. It has been well described 

 by Ogle.^ The flower-heads consist of an outer row of 



1 Pop. Sci. Rf.v. Arril 1870. 



Fig. 149. — Chrysanthemum Par- 

 tlieniwm^ "with enlarged ray 

 and disk florets and fruit. 



