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Areas suited to the production of sunflowers 4 Value of sunflowers in the semiarid regions 5 Soil relations and effect on the following crop 7 Varieties 7 Growing sunflowers for silage 9 Date of seeding 10 Method and rate of seeding 10 Cultivation and irrigation 11 Harvesting methods 12 Time to cut sunflowers 13 Filling the silo 15

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BULLETIN 981, U. S. DEPARTMENT OF AGRICULTURE. branches, and no rootstocks. Johnson grass {Andropogon lialepensis), on the other hand, is a perennial under favorable conditions, with stems more slender than those of Sudan grass, 3 to 4 feet high, few, narrow, rather harsh leaves which have thick white midribs, loose, open, often drooping panicles, few to many tillers, branching somewhat after maturity, and with numerous aggressive rootstocks which make it difficult to eradicate from cultivated fields. The seed characters of the two grasses will be considered in detail under 'Seed production." According to the classification of Piper in his '^Forage Plants and Their Culture," Sudan grass belongs to his proposed new agronomic group called^' grass sorghums," and its technical name is Andropogon sorghum sudanensis (19, pp. 33-34)^and not Andropogon Tialepensis, under which name it was obtained from Africa.^The dividing line botanically between Andropogon sorghum and Andropogon halepensis has been determined by Piper as the presence or absence of rhizomes, or rootstocks. This characteristic provides a very definite line of demarcation, and a study of the map of Africa and the Mediterranean region of Europe and Asia (fig. 3) leaves little doubt that the range of natural distribution conforms with this indicated classification.

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