COMPOUND FLOWEKS 123 



white or j^ellow. Of the former, the Daisy is an example ; the latter may 

 be seen in the Golden Rod and Corn-marigold. In one instance, the Yarrow, 

 both disk and ray are white ; and in some, as the Michaelmas Daisy, the 

 petals of the ray are purple. Several tonic and bitter plants, like the 

 Chamomile, are found in this group. 



The order of compound flowers is very extensive. The number of genera 

 is given by Hooker as 768, and of species as 10,000 ; the Compositse com- 

 prehend about one-tenth of all known plants, their proportions varying in 

 different parts of the world. In temperate regions they are mostly herbaceous 

 plants, but near the equator they are shrubs or trees. 



It should be noted that in the conspicuous grouping of otherwise insignifi- 

 cant flowers the Compositse show a considerable advance upon the Umbelliferre. 

 The success of this form of inflorescence is largely due in the Eadiatce to the 

 plan of enlarging the outer series of florets in order to make the flower-head 

 more attractive — a development of the method adopted by guelder-rose and 

 scabious. Most of the flowers in this order produce honey, and the anthers 

 shed their pollen before the stigmas are mature. Owing to the union of the 

 anthers a tube is formed into which the pollen is shed on top of the pistil. 

 Later the pistil divides at the top into two branches, the stigmas, but at first 

 these have their sensitive faces pressed together, and as the pistil lengthens 

 they act as a brush to push the pollen out of the anther-tube against the 

 bodies of insects that walk over the flower-head in search of honey. Insects 

 that visit Composites are therefore always more or less covered with pollen, 

 part of which they leave on the stigmas of older heads. Plants that matiu'e 

 their anthers first are termed proterandrous or protandrous, whilst those 

 in which the stigmas are developed first are known as proterogynous or 

 protogynous. 



Sub-order I. Chicory Tribe {Cichwacece). 



All the florets strap-shaped, having stamens and pistils. 



1. Goat's-beard (Tragojxjgon). — Involucre simple, of 8 — 10 long bracts in 

 one series, united at the base ; receptacle dotted ; fruit rough, with longi- 

 tudinal ridges tapering into a beak ; pappus feathery. Name in Greek signi- 

 fying a goat's-beard, from the bearded fruit. 



2. Ox-tongue {Helminfhia). — Involucre of about 8 equal bracts, surrounded 

 by 3 — 5 heart-shaped leaf -like bracts ; receptacle dotted ; fruit rough, with 

 transverse wrinkles, rounded at the end and beaked ; pappus feathery. 

 Name from the Greek, hehninthos, a small worm, from the form of the fruit. 



3. PiCRis. — Involucre of many compact and upright equal bracts, with 

 several small narrow ones spreading at the base ; fruit rough, with transverse 

 ridges, not beaked ; pappus of two rows, the inner one only feathery. Name 

 from the Greek pikros, bitter. 



4. Hawk-bit {Apdrgia). — Involucre with the bracts imbricated* 

 unequally, the outer scales smaller, black and hairy, in several rows ; 

 receptacle slightly dotted ; fruit tapering to a point ; pappus of one row, 

 feathery. Origin of name uncertain. 



5. Thrincia (Thrincia). — Involucre of several rows, the outer smaller , 



* Imhricaied, laid one over the other, like tiles on a liouse. 



16—2 



