THE VARIETIES OF FERTILISATION. 323 



(2) With regard to Reseda and EscJischoUzia, his observa- 

 tions are also somewhat misleading. Mr. Darwin experi- 

 mented with B. lutea and R. odorata. They are both very 

 capricious. Of R. lutea some individuals were absolutely 

 self-sterile, whether left to themselves or artificially polli- 

 nated, while a few produced self-fertilised capsules. Simi- 

 larly with R. odorata, when protected by a net some plants 

 were loaded with self-fertilised capsules, others produced a 

 few, and others, again, not a single one. Miiller,* however, 

 found that " plants which are kept protected from insects, 

 yielded capsules filled with good seed." The inference from 

 this variability in the fertility of different individuals in the 

 same year, is that it is an accidental peculiarity of some to 

 be more or less self -fertile than others ; and that it was due 

 to varying degrees of nutrition affecting the essential 

 organs. We know now that plants frequently vary in their 

 degrees of fertility, both at different seasons of the year,t 

 and in different years or localities, according to climate, con- 

 ditions of soil, etc. In any case, the self-sterility of these 

 plants is by no means so absolute as to justify the belief of 

 their having never been self- fertilised for years. 



Let us now turn to Mr. Darwin's experiments. 



Reseda lutea. The ratio between the heights of the crossed 

 plants and those of the self-fertilised were as 100 : 85, the 

 Aveights as 100 : 21, when the plants were grown in pots. 

 When grown in open ground they were nearer equality, viz., 

 in height, as 100 : 82, and in weight (a better test than 

 height), as 100 : 40. Differences in fertility are not given, 

 and, therefore, presumably not striking. 



* Fertilisation, etc., p. 116. 



t Mr. Darwin says Papaver vayum, incladed in the list of plants 

 sterile without insect aid, produced a few capsules in the early part 

 of the summer ; see above, Chap. XXV., on Sexuality and Environment. 



