Pitchered Insectivorous Plants . 
261 
pared it with a peltate Nelumbium leaf, and concluded that the 
lower solid part is the petiole, the pitchered part the leaf 
bearing on its front or dorsal side a flap-like excrescence 
comparable, he considered, to a ridge often seen on the outer 
base of peltate Nymphaeaceous leaves, while the lid represented 
a terminal leaf lobe. Asa Gray considered that ‘ they are 
evidently phyllodia’ and looked upon the lid as the leaf 
blade. For he says ‘in .S', variolar is the hooded summit 
answering to the blade of the leaf arches over the mouth.’ 
I will now try to show that a more natural and correct ex- 
planation can be given, one also in consonance with the other 
three genera. I have gone over the development of the adult 
leaf and find that, as in Nepenthes , each grows out at first as 
a little cone with concave basal part and rounded apex, below 
which a depression is formed. But even in very young leaves, 
between the concave area and slit-like depression a median ridge 
arises, which, as the leaf grows, gets greatly enlarged (Fig. 9 a). 
If the leaf becomes pitchered the cavity is formed in the 
midrib above the ridge, if it fails to pitcher the ridge develops 
as a large laterally compressed outgrowth of the midrib, and 
towards the apex it gradually curves into the midrib. Just 
beyond the point where it ceases a minute slit-like depression 
can be detected, so that, though some of the leaves of Sar- 
racenia may fail to produce a pitcher, they nevertheless show 
the rudiment of it. The basal depressed area becomes the 
leaf-sheath which is always strongly concave, while its bound- 
ing ridges become two rudimentary but very evident lateral 
lobes growing out from it. These gradually converging run 
face to face with each other and merge into the solid midrib 
above. But their applied faces are directly in line with the 
upper median wing, and a delicate groove continuous from 
the middle of their applied faces runs upwards on to the 
middle of it. I will now try to prove that this ridge is 
produced by fusion of what in Nepenthes are the widely 
separated dorsal flaps, and in Heliamphora the closely applied 
dorsal flaps. The leaf-sheath with its rudimentary lobes 
corresponds to the large green basal leaflets of Nepenthes , 
