40 
PACIFIC SCIENCE, Vol. XIX, January 1965 
foliage Ivs. 
Fig. 1 . Diagrammatic representation of change in leaf length along a single shoot in a diminutive species 
of Pandanus (P. I. 135008 U.S.D.A. Experiment Station, Miami, Florida). 
Sararanga they more or less completely enclose 
the axis at their insertion without forming a 
closed tube; there is no distinction between 
blade and sheath. In Freycinetia there is a slight 
differentiation between a short basal sheathing 
region and a blade, the mouth of the open sheath 
being slightly auriculate. 
GENERAL ANATOMY OF THE LEAF 
Leaf anatomy is very uniform throughout the 
Pandanaceae so that all leaves are basically con- 
structed alike, differences between different spe- 
cies being largely quantitative. 
The leaf is dorsiventral. Hairs are absent, al- 
though leaf margins and midrib usually bear 
prominent spines. Stomata are largely confined 
to the abaxial surface. The leaf is delimited by 
well-developed surface layers, each consisting of 
a shallow, strongly cutinized but never markedly 
thick-walled epidermis and well-developed, col- 
ourless, and often slightly thick-walled hypoder- 
mal layers, usually three or four cells deep. 
Adaxial hypodermal layers are usually somewhat 
thicker than abaxial. Epidermal cells are usually 
