On the Pitcher of Nepenthes : A study in the 
Morphology of the Leaf. 
BY 
F. ORPEN BOWER, D.Sc., 
Regius Professor of Botany in the University of Glasgow. 
With Plate XVI. 
HE ordinary method of morphological treatment ofleaves 
X is to distinguish from one another those parts, which can 
in very many cases be obviously recognised in the mature 
state with the naked eye, viz. the sheath, petiole, and lamina. 
This distinction of parts is commonly applied both in treating 
of simple and of branched leaves. 
Those who have studied the development of leaves have for 
the most part followed in the same lines, and have pointed out 
how, as a rule, the primordial leaf is differentiated at an early 
period into two parts, viz. the ‘ foliar base ’ or sheath, and 
‘upper leaf’ or lamina, while between these parts thus early 
distinguishable a subsequent process of intercalary growth 
results in the formation of the petiole. This method of dis- 
tinction of parts is maintained by most writers on the subject, 
whether the leaf be a simple or a, branched one. 
In a paper presented to the Royal Society in 1884 1 , 1 pointed 
out that this method of treatment of the leaf is at variance 
with our treatment of the shoot as a whole : that in thus dis- 
tinguishing sheath, petiole, and lamina, we lay stress upon the 
results of intercalary growth, which are regarded as only of 
1 On the Comparative Morphology of the Leaf, etc. Phil. Trans. 
[Annals of Botany, Vol. III. No. IX. May 1889.] 
