Ranunculus Bulbosus Scuiiplcnus. 261 



so give rise to a less steep curve, just as in the experiment 

 under consideration. 



I made a corresponding experiment in the summer of 

 1891, on the effect of manured and unmanured garden 

 soil, with the race w^hich was by that time consideraljly 

 improved (Fig. 51 and page 250). The manuring was 

 done with guano ; the two beds lay next to one another 

 and were of the same size. On each was sown half of 

 the harvest of several plants which had been very i)ro- 

 ductive of pleiopetalous flowers in 1890. In the course 

 of the summer 159 flowers on the unmanured bed opened 

 and were recorded and 376 on the manured. The rela- 

 tion between these two numbers is the best measure of the 

 effect of the manure. The results, reckoned in percent- 



Without manure the apex of the curve Avas over the 

 7 and there were very few flowers with more than eleven 

 petals : with manure the apex was over the 8, and there 

 were distinctly more pleiopetalous flowers. 



In both the above experiments the control material 

 consisted of other individuals than those used for the 

 experiment itself. It is possible, however, to subject the 

 same plant alternately to favorable and unfavorable in- 

 fluences, and when this is done the same result is ob- 

 tained as in the previous cases. With this object I trans- 

 planted a series of the best plants of 1892 to a very drv 

 bed in the spring of 1893. I left them there, and did 

 not water them although the weather was continuallv 

 dry. They suffered visibly under this treatment and 

 some of them even produced fewer flowers than in the 



