These features refer to the tenth leaf stage. The tenth leaf is the tenth true leaf produced after the cotyledons. On seedlings with alternate or spirally arranged leaves it is just simply the tenth leaf produced. On seedlings with opposite leaves it is one of the leaves in the fifth pair of true leaves produced. On seedlings with whorled leaves it will be one of the leaves in the appropriate whorl; e.g. if there are four leaves in each whorl then the tenth leaf will be one of the leaves in the third whorl.
There are two basic leaf types: simple leaves and compound leaves. Simple leaves have buds or shoots in all forks formed by petioles and the stem. Compound leaves appear to have neither buds nor shoots in the forks formed by what appear to be the petioles and the stem. This results from the fact that the apparent leaves are in fact leaflets, and constitute a portion of a compound leaf. The leaf proper consists of a number of leaflets, and a central stem-like axis to which the leaflets are attached. Buds and new shoots occur in the fork formed by the compound leaf axis and the true stem.