260 Non-Isolablc Races. 



flowers^ (like the small, late-germinating seeds of the 

 crimson clover), or germination in the height of the 

 summer in better and particularly in warmer weather 

 favors development in such a way that the flowers are 

 richer in petals ; for the plants which flowered in July 

 and August, germinated for the largest part during the 

 cold and unfavorable weather experienced in May shortly 

 after they had been sown. 



I first made an experiment to determine the influence 

 of nutrition on pleiopetaly in 1890. I had wintered the 

 selected plants of 1889, and in ]\Iarch transplanted half 

 of them on a bed of pure sand, and the other half on a 

 bed of ordinary garden soil. Only two-thirds (i. e., 12) 

 of the plants of the former lot flowered, whilst all of the 

 latter did. On the sandy bed I counted the petals of all 

 the flowers and about twice their number on the control 

 bed by simply picking off all the open flowers on alternate 

 days. I examined in all 75 and 147 flowers respectively. 

 The following is the result reckoned in percentages for 

 convenience of comparison : 



The plants on the better soil produce distinctly fewer 

 five-petalled and more 7-10 petalled flowers. It is per- 

 haps permissible to conclude from this that the steep drop 

 of the curve from the wild locality, where the soil was 

 sandy is, to a large extent at any rate, due to low nutri- 

 tion. For presumably the same plants would exhibit a 

 higher degree of pleiopetaly if grown on better soil and 



* With regard to this, it would be of great interest to find out in 

 this and other plants the degree of development of the anomaly in 

 such individuals which do not germinate until two or three years 

 after the sowing of the seed 



