314 Origin of Each Species Considered Separately. 



The forms of the petals of a single flower often differ 

 from one another (Fig. 59 b). The petals of plants 

 grown in the field on dry sand were narrower than those 

 of plants grown in the garden on manured soil. The 

 petals of the former were almost twice as long as broad, 

 in those of the latter the relation of length to breadth 

 was as 2 to 3. The emarginate character of the normal 

 petals is absent in them; the petals are, on the contrary, 

 obtusely rounded. Their greatest breadth is in the middle. 

 The narrowest petals that I have observed were three 

 centimeters long and one broad. But as I have already 

 stated there exists a complete series of transitions be- 

 tween these and the obcordate ones of strong flowers. 



Oval petals are by no means confined to O. laevi folia. 

 They occur regularly on O. elliptic a. I have also some- 

 times found them on weak shoots of 0. biennis. 



In the other characters 0. laevifolia is very much 

 like O. Lamarckiana, not differing from it in any essen- 

 tial features save those already mentioned. The plants 

 are about the same size. So are the flowers and fruits 

 and general habit. Nevertheless a bed of 0. laevifolia, 

 even if it is some distance away can always be recog- 

 nized from a group of Lamarckiana by characters which 

 may be manifested to a greater or lesser degree but 

 which always tend in the same direction. The color of 

 the flowers, especially of the later ones, is usually a little 

 paler; the buds a little thinner, the bracts of the inflor- 

 escence a little narrower and the whole plant more deli- 

 cate and neat. 



During the first few years of its cultivation I used 

 to allow O. laevifolia to cross freely with O. Lamarckiana 

 for reasons which I have mentioned above (§6). But 

 since 1894 I have excluded the visits of insects by en- 



