(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.
(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