304 Non-Isoldble Races. 
amounts employed in this experiment (about 80 grams 
per square meter) should not be exceeded, that is to say, 
that the result cannot be improved by still heavier ma- 
nuring. 
For the experiment with sand I dug in my experi- 
mental garden a bed of 13 square meters in extent and 
one-half a meter deep, and filled it with ordinary fine 
sand. On this bed and on a neighboring one of the same 
size I sowed seed of Oenothera Lamarckiana in the sum- 
mer of 1899. The control bed was not manured but 
contained a very fertile soil ; the seed was sown in the 
middle of April. 
The sand of the bed bordered immediately on the 
rich soil of the path which surrounded it. 1 Therefore 
the plants at the margin could thrust their lateral roots 
into this, and thus obtain richer food than the more 
central rows. This circumstance showed very important 
results during the course of June, for while many flower- 
ing stems were produced towards the outside of the bed, 
hardly any occurred in the middle. It was not until the 
middle of July that the development of stems set in here 
also. Curiously enough this occurred in almost every 
instance at exactly the same time. In the middle of 
August among the 82 plants of the outer rows about 
60% had developed stems, whilst in the middle there 
were 133 rosettes amongst 203 plants, that is to say 
about 24% of annual specimens. We see that the dis- 
tances between the plants in this experiment were very 
considerable, for on 13 square meters there were only 
285 plants. Even at the end of the summer they hardly 
touched one another. In the control experiment in which 
1 In subsequent years I have separated the sand from the earth 
by bonrds. 
