26 



agency of an nndci-gronnd stem, similar to the well-known 

 pointed, white and jointed underground stem of witch grass, 

 which is so frequently pictured as growing through a potato, 

 for example, and which is generally so well known. Those 

 underground stems extend through and through the ground 

 in the neighborhood of the plants from which they start. 

 They are jointed, and provided with roots springing from 

 near the joints. At each joint there is a bud from which a 

 new stem pushes up into the air. From this centre a new 

 plant is formed. This in turn produces underground stems, 

 and the soil is gradually filled fuller and fuller of such 

 stems, crowding through it in all directions and all sending 

 up new stems from the joints. In the case of all the sod- 

 forming grasses, then, the tendency is for the turf to become 

 constantly thicker, closer and finer. The surface of the 

 ground is completely covered, and a thick, tough sod of 

 turf, firmly held together by the underground stems and by 

 the roots, is formed. Grasses of this character are persist- 

 ent, and they are not likely to die out under the action of 

 natural causes nor to be crowded out by other species. 

 Among such grasses meadow fescue and tall meadow fescue, 

 Kentucky blue-grass, awnless brome grass and redtop are 

 the more important. 



There are a few grasses wdiich spread and form a turf grad- 

 ually thicker and thicker, by rooting at the lower joints of 

 the stem. The stems of such grasses incline to bend near 

 the l)ase, so that the lowermost joint and jierhaps the second 

 joint also comes to rest on the surface of the ground. Under 

 these circumstances, if the soil is moist, roots are sent out 

 from the joints in contact Avith the ground, and thus the 

 plant spreads and gradually forms a turf which becomes 

 thicker and thicker with the lapse of time. The bent grasses 

 are of this description. Grasses having this habit, like those 

 having the underground stems which have been spoken of, 

 are persistent. 



The non-sod-forming grasses are not provided with either 

 of these means of renewing themselves. Each plant conies 

 from a seed. The jdant, originally small, gradually increases 

 ill size, until fntiii a single root a very considerable number 



