35 ° Sutherland and Eastwood . — The Physiological 
geotropism, and thus occupy newly deposited strata. The rhizome, whose 
length varies with the substratum, differs little from the ordinary grass type, 
as also the erect haulms. Rigidity is aided by the long-continued invest- 
ment of the stem by the leaf sheaths. The long, rigid, semi-erect leaves 
belong to the furrowed type, rolling to a limited extent and showing a dis- 
tinct pulvinar action at the articulation. The ligule also possesses a kind 
of pulvinus. 
Anatomy . — The epidermis shows great local variations in the outline, 
arrangement, thickening, and structure of its units. Exposed portions have 
a distinct waxy coating overlying thickened and cutinized walls. The 
adaxial surface of the leaf-blades possesses papillae which aid the wax in 
preventing wetting. 
The most active stomata, which occur on the sides of the furrows, show 
interesting auxiliary structures in the form of forked papillae on the sub- 
sidiary cells. These bend over the slit, forming a fringe which entangles 
an air-bubble when the leaves are submerged, and thus prevent the flooding 
of the air-spaces. The other stomata are of the normal grass type, but in 
some positions they are inert, owing to the absence of chlorophyll and the 
small osmotic content of the guard cells. 
Numerous hydathodes of a hitherto undescribed type occur along 
definite tracts in the neighbourhood of large water-storing cells. These 
excrete large quantities of water and salts in solution. This exudation is 
due to some form of protoplasmic activity within the hydathode rather 
than to root pressure. 
Hairs are abundant on the young vegetative organs, but most disappear 
very early. They persist on the glumes, where they may help in the 
opening and closing of the flower, and also in entangling air-bubbles when 
submerged. 
There is a large development of air-passages in all organs of the plant. 
Their origin varies in different parts. 
The two types of roots show differences in thickening and the degree 
of air-passage formation. A remarkable feature is the presence of solid 
portions in the deep penetrating roots, where numerous air-passages would 
seem more in keeping with accepted views. 
In conclusion, we wish to express our thanks to Dr. O. Stapf and 
Mr. L. A. Boodle for helpful suggestions and criticism. We are also 
indebted to the Director of Kew Gardens for permission to work in the 
Jodrell Laboratory, where part of this work was completed. 
University College, 
Southampton. 
