Alternating Annual and Biennial Habit. 303 
as annuals, and of late I have grown all my cultures by 
this method or by some .slight modification of it. 
In order to determine the effect of the soil on the 
development of the stem I have compared the difference 
between plants grown on manured and unmanured beds, 
and also the difference between plants grown on barren 
sand and on fertile soil. The first of these two experi- 
ments I have made with the Oenothera laevi folia. I 
used seeds which I had saved in 1890 from the third 
annual generation of my culture (see Vol. I, p. 273). 
The seeds were sown in the middle of May on three 
beds of 3 l /4 square meters each. They were adjacent to 
one another, had the same soil, a similar exposure, and 
so forth. The seedlings were thinned out early, to 100 
per bed, in such a way that the distances between them 
were as uniform as possible. The sole difference lay 
in the kind of manure which they received, which in 
No. 1 was nothing, in No. 2 a quarter of a kilo of guano, 
and in No. 3 a quarter of a kilo of hornmeal. In the 
second bed, therefore, the manure was rich in phosphates 
and in the third in nitrogen. On the 30th of July 1 
recorded the plants with the following result : 
PLANTS ANNUALS 
No. 1. Without manure 100 17% 
No. 2. With guano 98 90% 
No. 3. With hornmeal 108 94% 
In spite, therefore, of the fact that the race had been 
selected for three years the proportion of annual plants 
on the bed without manure was only 77 per cent, whilst 
this proportion was considerably increased by the addi- 
tion of manure, and more by the addition of nitrogen 
than by that of phosphates. Further experiments with dif- 
ferent quantities of the same manure showed that the 
