In the branch systems of grasses, each lateral shoot bears a bikeeled first leaf (prophyll) facing the axillant leaf and addorsed to the main axis (Fig. 182, B, p. 356). Opinion has been divided, in the past, as to whether this bikeeling indicates a derivation from two leaves, but the more recent evidence seems to me to favour the view that the prophyll is a single leaf, whose characters are those of a leafsheath. It probably owes its curious form to the pressure due to space conditions in the bud. Although the prophyll has two principal bundles, its symmetry is not really duplex, for one of the bundles is, as a rule, earlier in development, and larger, than the other. Moreover the bud axillary to the prophyll tends to occur opposite to this larger strand, which may thus, on all counts, be interpreted as the median bundle. These points are illustrated in Fig. 142, p. 280, and Fig. 143, A2 a−A2 c. p. 281. In one or more of the earliest leaves succeeding the prophyll, the sheath is apt to predominate, while the limb is absent or reduced (cf. Fig. 131, A, p. 265).

The mode of origin of the leaf members from the stem apex in grasses is a matter of some interest. A few years ago, it was reported that in Wheat the leaves develop from the dermatogen alone, whereas, in other families, not only the dermatogen, but deeper layers as well, play a part in leaf production.