1052. When a seed has germinated, the root appears first, probably as it is through the root only that the plant can obtain food from the soil. The part between the collar and the cotyledons, which is called the caulicle, then begins to lengthen, straightening itself, if it chances to be bent by the seed being badly placed, and generally raising the cotyledons out of the earth, frequently with the integument or outer covering of the seed still attached to them, especially in the commoner species of the pine and fir tribe. When the cotyledons are raised above the surface they soon expand, and, becoming green, act as leaves. Sometimes, however, the cotyledons never escape from the integument of the seed, but remain buried with it in the ground; and in this case the base of the cotyledons lengthens, so as to allow the plumule to escape from between them, as in the Araucaria imbricata. (See Elements of Botany, p. 116.)
