SUDAN GRASS AND RELATED PLANTS. 55 
may grow sufficient seed for his own plantings and thus be assured of 
its purity; (2) that if the farmer finds it necessary to buy Sudan grass 
seed and his land is free from Johnson grass, he should purchase 
only seed grown outside the Johnson grass region or from responsible 
growers in the South who are willing to guarantee its purity; (3) and 
that if the Sudan grass is to be seeded on land already foul with 
Johnson grass the presence of seed of the latter is a matter of small 
importance. 
The southern planter can afford to pay a slight advance in price 
for seed produced north of 38° north latitude or by responsible 
growers south of that parallel. (See the map, fig. 13.) It must be 
remembered, however, that some of the Sudan grass seed handled 
by northern seedsmen is purchased by them in the South, so that 
to be absolutely safe the seed must be registered as northern grown, 
and even then it will not be pure unless the grower has sown seed 
free from Johnson grass seed and other impurities. 
The Texas Agricultural Experiment Station has done more to 
safeguard the production of Sudan grass seed than any other agency 
in the United States. Through the Texas Experiment Association, 
an organization intended to assist in all movements to improve agri- 
cultural conditions, a campaign was launched in 1914 to require 
each bag of Sudan grass seed to be labeled with the name and address 
of the grower, together with information as to the grade of the seed 
and whether it had been inspected in the field by a representative 
of the association. Instructions regarding the proposed grades of 
seed and the methods of tagging the package offered for sale were 
issued by the secretary of the association on August 3, 1914. Much 
good was accomplished by this effort in stimulating the production 
of pure seed and in acquainting farmers with the extreme care required 
in such work. | 
DESCRIPTIONS OF THE SEEDS OF SUDAN GRASS AND JOHNSON GRASS. 
The seeds of Sudan grass and Johnson grass resemble each other 
so closely that it becomes a matter of extreme difficulty to detect the 
presence of small numbers of Johnson grass seeds in the seed of Sudan 
erass. Bulk lots of Sudan grass seed are easily distinguished from 
Johnson grass seed on account of their uniformly larger size (fig. 23), 
but the variations in size, color, and other factors of appearance are 
so slight that individual seeds may be indistinguishable except under 
very close examination and with the aid of a magnifying giass. 
Certain points of difference in the seeds of these two grasses were 
pointed out, first by Oakley in 1912 (18, p. 504) and later by the 
senior writer (23). No critical investigation of this rather important 
question was attempted, however, until it was necessitated by the 
action of horticultural inspectors in certain California counties, who 
refused to allow the importation of Sudan grass seed, claiming that 
