AGGREGATE. 



567 



shorter or longer tube, not always of the same bore throughout 

 and especially slightly widened at the top to form a bell-shaped 

 opening, with 5 regular teeth : (b) labiate after f , i.e. with 2 

 petals in the upper and 3 in the under lip : (c) ligulate, i.e. the 

 corolla is split for a considerable distance on the posterior side (as 

 in the Labiate genus Teucrium} and prolonged into a long, strap- 

 like portion (Fig. 609 A), which projects upwards. A distinction 

 must, however, be drawn between the true and false ligulate 

 corolla. In the first case the corolla has 5 teeth at the apex (Fig. 

 609 A) and is made up of all the petals of the corolla united 

 together ; this is the usual condition in the Ligulate-flowered. In 

 the latter case (Fig. 605 G) the tongue has only 3 teeth (or is 

 more irregularly 2-3-dentate), and is only formed of 3 petals ; 

 the corolla is then truly bilabiate, the tongue is the large under lip, 

 and the upper lip is very slightly developed, or even at an early 

 stage quite suppressed. This false " ligulate" corolla is found 

 among the rtiy-flowers ; sometimes the upper lip is seen quite 

 plainly, e.g. in Tagetes, especially in the double capitula. The 

 VENATION of the corolla is peculiar ; there are always comrnisural veins which 

 branch dichotouiously at the angles between the teeth of the corolla, and send 

 a branch into the edge of the two nearest teeth. The midrib is frequently 

 absent, but may be present, and then it has sometimes no connection with the 

 other veins of the corolla. 



The STAMENS are attached to the corolla, and have free 

 filaments (Silybum has united filaments), but the anthers, which at 

 first are free, adhere together and form a tube (Fig. 605 E : only 

 'Ambrosiese have free anthers). The connective is generally pro- 

 longed, and protrudes above the anthers 

 as a thin, brown membrane of various 

 forms (Fig. 605 E) ; appendages of 

 various forms may also be found at the 

 base of the anthers. The anthers open 

 introrsely, and the pollen must be carried 

 out at the top of the tube by upward 

 growth of the style, and by means of the 

 "stylar-brush" (Figs. 607, 608, 609) ; the 

 filaments are sometimes sensitive (e.g. in 

 the Corn-flower, Fig. 607), and shorten 

 on being touched, so that the anther- 

 tube is pulled downwards, and the pollen 

 swept out at the top (Figs. 607, 608 

 A,B). 



A B 



FIG. 607. Centaurea cyanus : 

 A the anther-tube (.--t) with the 

 crescentic curved filament be- 

 fore irritation ; g the style ; 7; 

 the base of the corolla; B the 

 same after irritation, the an- 

 thers are drawn further down. 



