From the Southwest.
Grenada, Miss. April 12
--Large reinforcements and commissary and quartermaster's stores have arrived.
The new plan is to send a force to each of the three railroads coming South.
Grant's army joins Rosecrans by water.
The Tennessee is falling rapidly.
[The above is supposed to refer to the plans of the enemy, but it is difficult to render it intelligible.]
Hernando, Miss, April 11--Ellett's Marine Brigade has certainly gone to Memphis.