(3) It is suggested, contrary to what is. generally believed, that the true function of the motor -cells in grasses is that of creating 'accommodation gaps' to permit of enrolment. The actual mechanism which brings about the movement is differential turgor on the adaxial and abaxial sides. The lower surface is usually strongly cutinised. in enrolling types, and the stomata are principally situated on the upper surface. The upper mesophyll cells lose moisture more rapidly therefore, and cause the upper surface to shrink. The motor -cells lose their water content to the mesophyll cells and by providing longitudinal lines of weakness facilitate enrolment.

(1) Cross sections of the leaves present a valuable means of identification of grasses in non -flowering condition in most cases. Even, when inflorescence is present, this method will prove of material assistance in making a determination. There is sometimes considerable differences anatomically, between cuíim and basal leaves. It is important, therefore, that basal leaves only be utilised for purposes of diagnosis.

(2) The anatomical structure does not appear to undergo change with alteration of habitat, though the leaves themselves may be smaller or larger according to the suitability of the habitat,. and leaves which are as a rule permanently enrolled exhibit a tendency to remain partly expanded.