PROPAGATION OF PLANTS 39 



these plants as perennials, but they are a very different 

 kind of perennials from alfalfa and trees. 



The grasses with long stolons, like blue grass, tend to 

 form a dense sod, and are, therefore, best for pasture. The 

 less strongly stoloniferous kinds, as timothy, are usually 

 best for hay; probably because the dense sod developed 

 by the strongly stoloniferous species contains so many 

 stems that none of them can grow large enough to produce 

 a good hay crop. 



36. Roots. The edible portion of the sweet potato is 

 an enlarged root. The potato plants are grown from these. 

 The roots are put about an inch apart in hotbeds, with 

 about four inches of dirt under them and two inches on 

 top. The roots send up many sprouts from adventitious 

 buds. When these shoots have reached the proper height, 

 they are pulled. This permits the potato to send up more 

 sprouts. The plants thus grown will have a good supply 

 of roots of their own before they are pulled from the 

 potato. Sweet potatoes are also grown from cuttings 

 taken from the vines produced by the earlier plants. 

 Occasionally, the potatoes are cut into pieces and planted 

 like Irish potatoes. 



37* Tubers. The field, or Irish potato, is a modified 

 stem. The eyes send out branches, so it might be propa- 

 gated in the same manner as the sweet potato, but this 

 is not profitable. 



Irish potatoes are usually cut into two or more pieces 

 for planting. The larger pieces have given the larger yields 

 in most experiments. Of ninety-five experiments reported 

 from various experiment stations, seventy-six found that 

 half-potatoes yielded more than those cut to two eyes, 



