On the Leaf-tips of certain Monocotyledons.



In the present paper the leaves of Monocotyledons are treated from the standpoint of the Phyllode Theory—that is to say, it is assumed that these leaves include no region equivalent, morphologically, to the lamina of the Dicotyledon.

It is concluded on the evidence of comparative morphology and anatomy that, in the case of simple Monocotyledonous foliage-leaves terminating in a solid apex, and also in the case of spathe-leaves ending in a similar tip, the main part of the leaf is of leaf-sheath nature, while the apex represents a vestigial petiole.

In the case of those more complex Monocotyledonous leaves which are differentiated into sheath, stalk, and “blade,” certain cases are known in which the “blade” terminates in a solid apex. It is provisionally suggested that such apices represent the unexpanded tip of the petiole: in other words, the main part of the distal region of the leaf-stalk has developed into the “pseudo-lamina,” while the extreme tip has remained relatively unmodified, retaining its solid petiolar character.