126 THE FLOWERING PLANT. 



nectar is excreted deep down between sepal and style, and the 

 bee, in backing out, rubs its head against the anther. The little 

 shelf is not stigmatic below, and is simply lifted up out of harm's 

 way for a moment. 



The most daring way by which self-pollination is avoided by 

 regular flowers is where the style actually assists in the distribu- 

 tion of pollen. This is seen in harebell (and Canterbury bell) and 

 many Composites. In the former case the anthers shed their 

 pollen before the flower opens, and a great deal of it adheres to 

 the hairy outer surface of the style. Later on, the three (or 

 more) lobes in which the style terminates expand and display 

 their stigmatic inner surfaces. 



The regular disk florets of a daisy or sunflower will illustrate 

 the method in many Composites, and show the meaning of 

 syantherous stamens. Take, for example, a half-blown example 

 of the larger form. The youngest inner florets are still shut. 

 Outside these come a large number in which the brown anther- 

 rings are very conspicuous. Dehiscence is internal, and by 

 looking at older and older florets (i.e., passing gradually to the 

 outside), you will find that first a small heap of pollen is seen on 

 the top of the anther, and then the elongating style gradually 

 emerges. It is provided with a little brush of hairs at its end, 

 and, in fact, sweeps the pollen clean out of the tube, afterwards 

 spreading into two lobes, stigmatic, as will be anticipated, inter- 

 nally. The most external disk-florets will be found already 

 pollinated, with stigma and stamens withered. Aggregation 

 not only renders Composites conspicuous, but also makes them 

 favourites with insects, since a great deal of nectar is attainable 

 in a small area. Their visitors alight in what must relatively 

 be a perfect thicket of anthers and stigmas in various stages. 

 Cross-pollination cannot but be extremely frequent. 



II. Irregular Flowers. — Larkspur contrasts strongly with the 

 closely related buttercup. Bees alight on the large petaloid 

 sepals (cf. p. 85), and to reach the nectar contained in the two 

 spurred petals, must pass their tongues through a small opening 

 between the upper leaves of the perianth. Now the principle 

 alluded to on p. 121 comes into play. The stamens mature first, 

 and successively raise themselves into this opening, retiring 

 afterwards. Lastly, the stigmas are lifted up into the same 

 position. 



Indian-cress (so-called garden nasturtium) works on the same 

 lines, but the nectar is here contained in the spur of the gamo- 

 sepalous calyx. 



Papilionaceous flowers present many interesting modifications. 

 In all of them the wings (cf. p. 88) serve as a landing-stage, 



