SWEET-CLOVEE SEED. 23 
normal in July. Both the precipitation and temperature were about 
normal at Ames in August, but most of the precipitation fell before 
the experiments were commenced. 
In north-central Illinois the seed production of sweet clover was 
very irregular. Some fields produced an abundance of seed, while a 
large percentage of the pods on the plants in other fields near by, 
where the thickness of the stand, size of the plants, and conditions 
in general were approximately the same, aborted. It was evident 
that all stands producing a good seed crop were growing on well- 
drained soil and that those which were not yielding satisfactorily 
were on poorly drained land. It is well known that sweet clover 
will produce deep taproots only when the plants are growing in 
well-drained soil and that a much-branched surface root system will 
be formed on poorly drained land, and especially when there is an 
excess of moisture or a high water table during the first season's 
growth. During this droughty period in 1916 the upper layer of soil 
became so depleted of moisture that the plants with surface root 
systems were unable to obtain sufficient water to mature their seed. 
On the other hand, the lack of precipitation and the high tempera- 
tures did not affect the moisture content of the subsoil sufficiently 
to interfere with the normal seed production of deep-rooted plants. 
According to Lutts (22, p. 47) this same condition was found to be 
true in Ohio in 1916. 
As a rule, under droughty conditions the second crop of sweet 
clover will produce a higher yield of seed than the first crop, as the 
second growth of the plants is seldom more than half as much as the 
first, thereby requiring less moisture. However, if showery hot 
weather prevails when the first crop is cut, the end of each stub is 
very apt to become infected, usually with a species of Fusarium, 
which kills all the cortex as far back as the upper bud or young shoot 
and that part of it on the opposite side of this bud to the bud below. 
If the second bud from the top of a stub is not directly opposite the 
upper one the decay may extend nearly to the ground. (PL IV.) 
The destruction of half to two-thirds of the cortex from 2 to 4 inches 
below the upper bud materially reduces the quantity of water that 
can be conveyed to the branch above the base of the dead area. 
Plants thus infected obtain sufficient moisture for seed production 
only under the most favorable conditions. When the first crop is 
cut during warm dry weather, and especially when the first crop has 
not been permitted to make more than a 30 to 32 inch growth, the 
stubbie seldom decays, and in no instance have the plants been 
observed to decay as far back as the upper buds. 
An experiment was conducted at Ames in the latter part of August 
and first part of September, 1916, to determine the effect of watering 
plants that were aborting a large percentage of their flowers and 
