376 Origin of Each Species Considered Separately, 



smaller in correspondence with the greater weakness of 

 the whole plant. The petals commonly measure only 2% X 

 4 cm., as opposed to the 3X5 cm. of Lamarckiana. 



On annual plants some of the flowers are often in- 

 completely developed. As a rule only one or two flow- 

 ers on a plant are affected in this way. Sometimes there 

 is very little pollen, sometimes none at all; very often 

 it happens that the stigmas cannot separate, and remain 



close together. This stig- 

 matic group is often 

 quite small and . some- 

 times blackens and shriv- 

 els up before pollination. 

 Or again, the style may 

 be so short that it does 

 not protrude from the 

 corolla.^ 



A striking abnormal- 

 ity is an oblique position 

 of the buds on the calyx 

 tube (Fig. 80). The 

 calyx is bent sideways 

 in such a manner that 

 the bud is at right an- 

 gles to the calyx tube. 

 The opening of the calyx is interfered with by this and 

 indeed often takes place abnormally or incompletely. The 

 petals do not unfold properly and the sexual organs are 

 more or less sterile. 



These abnormalities are usually to be found on the 

 lower flowers when the plant has not attained a height 



_^ These and other malformations of the dwarfs are often due to 

 a disease, and as such, to a large degree dependent on outer circum- 

 stances. (Note of 1908.) 



Fig. 80. Oenothera nanella. Buds at 

 the top of the stem. At the side 

 are shown the commonest malfor- 

 mations of such buds. 



