COMPOSITE 101 



are very broad and winged, and, notwithstanding the width 

 and elevated character of the receptacle, comparatively 

 few reach maturity. On the other hand, the distribution of 

 the fruits which do mature is aided by wing-like develop- 

 ments of their edges. These facts are borne out by other 

 species examined, of which a description is given below 7 . 

 Another very noticeable fact is that a larger proportion of 

 the fruits of annual species seem to reach maturity than in the 

 case of perennials. The fruits of Bidens humilis and B. leu- 

 cantha are very narrow, and a large percentage of them reach 

 maturity. Both are annual species, and the barbed character 

 of the pappus of some, including B. leucantha, is well adapted 

 to ensure the distribution of the fruits. 



The polymorphic forms of the fruits of Calendula even on 

 the same receptacle are very remarkable. In C. officinalis 

 at least three very distinct types may be noted. Two or three 

 rows round the margin of the receptacle consist of greatly 

 elongated, curiously constructed, curved achenes, muricate on 

 the back, often beaked at the apex and produced into a hook- 

 like process near the base on the inner face. The middle set 

 of fruits is furnished with broad wings involute at the mar- 

 gin, but neither beaked at the apex nor produced into a foot 

 at the base. Those about the centre of the receptacle are 

 greatly incurved, often forming a complete ring, and have 

 narrow wings involute at the margin. Transverse sec- 

 tions of each series give a good idea of the structure of the 

 three different forms. The embryo is cylindrical in all three 

 cases, curved, gradually tapered into the radicle, and other- 

 wise similar except that the middle series is not so strongly 

 curved. 



It would seem as if we have here three devices for pro- 

 moting dispersion this being effected in the outer seeds by 

 the presence of a hook, the intermediate ones by means of a 

 wing, and those in the centre by resemblance to an insect. 



During germination all three kinds behave in a similar 

 manner, except that in the broadly winged fruits of the middle 

 series the radicle (fig. 477) runs along the groove formed by 

 the strongly involute wings till it reaches the apex of the fruit 

 when it turns downwards and enters the soil, firmly fixing the 



