BETTER ADAPTATION OF PLANTS 355 
Everyone may not agree with this order, but I have placed what 
I consider the most undesirable first on the list. Bromus rigidus 
is a borderline grass. it is palatable and nutritious when young, 
but the ripe panicles are obnoxious because of the barbed awns on 
the seeds which do not readily shatter. For this reason it is placed 
in the “undesirable” column. 
In some fields, undesirable species may comprise 90% of the 
ground cover. What method of weed control can be used to change 
this balance? No chemical has yet been developed that will per- 
form this miracle. 
It was customary in the early days in California, as elsewhere, 
to turn animals into a field or area and leave them there as long 
as possible. In the fall there was a scarcity of feed, but in the early 
spring, an excess. Since the introduced annuals spread so rapidly, 
this grazing system must have favored them. Given free choice, 
animals will select and choose their forage plant by plant. As the 
more palatable plants are consumed, livestock turn to the less 
palatable ones. 
Continuous use, then, favors the less desirable species. It should 
be obvious, then, that 1f we want to discourage such weedy an- 
nuals, we must change our harvesting program. 
Experiments to test this idea were reported by Love (34) and 
Jones and Love (33). Both mowing and grazing were used. In a 
clipping experiment half of each of twenty-four plots of Spa, 
seeded in the fall of 1942, were mowed April 1, 1943, and the other 
half, May 13, eae about six weeks later. Counts made in Janu- 
ary, 1944, showed a reduction of 30% in stand in the first set 
compared with a 71% reduction in the late-clipped plots. 
In the second experiment fall seedings were subjected to inten- 
sive grazing by sheep at two different dates, beginning April 2, 
1943, and April 20, 1943. Plant counts were made September 23, 
1943. Eight perennial grass species in plots totaled 255 plants in 
the first field and only 75 in the second. Apart from actual num- 
bers, those plants in the first field were healthy and vigorous at 
the end of the dry season in 1943, whereas those in the other field 
were poorly established with weak root systems, barely holding 
the crowns in contact with the soil. Love wrote (34): “‘The fact 
that during this critical period (1.e., the first spring following 
