COMPOSITAE 167 



may he put down perhaps to the concurrence of several useful 

 peculiarities, viz. 



1 i) the massing of the fls. in heads, surrounded by invol. bracts: 

 from this there results 



(a) greater conspicuousness, especially when ray-florets are 

 developed; (A) a saving of material in the corollas, &c. ; 

 (c) the fact that one insect visitor may fertilise many 

 fls. in a short time without having to fly from one to 

 another ; 



(2) the very simple and effective floral mechanism, which ensures 

 (</) protection of honey and pollen ; (e) exclusion of the very 



short-lipped (allotropous) insects, but not too great speciali- 

 sation for a very narrow circle of visitors ; (f) prevention 

 of self- and chance of cross-fertilisation till the last possible 

 moment; (g) certainty of self-fertilisation if the cross 

 fails ; 



(3) the use of the calices of individual fls. for purposes of 

 seed-distribution, and the very perfect character of the 

 mechanism. 



These considerations should be compared with the features of rival 

 fams., e.g. Cruciferae, Gramineae, Rubiaceae, Leguminosae. 



Economic uses. The C. furnish but few useful plants (other than 

 border or greenhouse pi.). See Lactuca, Cichorium, Cynara, Heli- 

 anthus, Carthamus, Chrysanthemum, Tanacetum, &c. 



Classification and chief genera (after Hoffmann). The classifi- 

 cation of the C. and the determination of their genera is a matter of 

 no small difficulty ; we shall give only the primary groupings and their 

 chief genera. [There are several exceptions to the characters given 

 below.] 



{Abbreviations : cap. = capitulum ; tub. = tubular ; lig. ligulate ; 

 homog. = fls. in head all similar as to sex; heterog. = fls. of different 

 sex in one head, e.g. ray ? and disc .] 



A. TUBULIFLORAE. Fls. of disc not ligulate. No latex. 



1. Vernonieae (cap. homog. ; fls. tub., never yellow; anthers 



arrow-shaped at base, pointed or rarely tailed, with 

 filaments inserted high above the base ; stigmas semi- 

 cylindrical, long, pointed, hairy outside) ; stigmatic 

 papillae all over inner surface : Vernonia, Elephant opus. 



2. Eitpatorieae (cap. homog.; fls. tub., never pure yellow; 



anthers blunt at base, with filaments inserted at base; 

 stigmas long, but blunt or flattened at tip, with very 

 short hairs ; stigmatic papillae in marginal rows) : Age- 

 ratum, Eupatorium, Mikania, Adenostemma. 



3. Astereae (cap. heterog. or homog.; all or only central fls. 



tub. ; anthers as in 2 ; stigmas flattened with marginal 

 rows of papillae, and terminal hairy unreceptive portions): 

 Solidago, Bellis, Aster, Erigeron, Baccharis, Callistephus, 

 Olearia. 



4. Imileae (as 4 ; qorolla in tub. fls. with 4 5-toothed limb ; 



anthers tailed at base ; styles various) : Blumea, Filago, 

 Antennaria, Gnaphalium, Helichrysum, Inula. 



