Insectivorous Plants ( Part II). 451 
ferous, Acanthaceous, and even more ancient alliances like 
the Ferns, are too numerous to admit of doubt. Complete 
verification of the position is furnished by leaves of Gleditschia 
triacanthos. In addition to the ordinary pinnate leaves that 
appear chiefly on shoots from second year's wood, and the 
bipinnate, more rarely pinnate, leaves that spring from the 
first year’s wood, hundreds of examples can be got from 
a single tree, where every transition-stage, from an entire 
leaflet to one cut up into secondary leaflets, is presented. 
Some of these are illustrated in Figs. 38-43, and clearly 
prove that leaflets, historically, are restricted parts of an 
originally continuous lamina or c wings of the phyllopodium.’ 
Localized growth of one region is usually associated with 
intercalary or apical growth of another, and thus leaf- 
indentations, leaf-lobes with broad insertion on the mid-rib, 
and leaf-lobes with narrow insertion (so-called ‘pinnae’) are 
transitional phases in leaf-modification. To fix on any one 
of these in its earlier development, and arbitrarily separate 
it from the others, no matter what the subsequent history 
is, can only obscure the true issues. On this account I would 
designate as leaflets any portions of the originally continuous 
lamina, or ‘ wings,’ which become completely isolated along 
the mid-rib at any period of development up to the stage 
when maturity is reached. Certainly it might be convenient 
for descriptive purposes to use terms, as is actually done, 
that would approximately indicate stages in leaf-division, 
but at best these would be inconstant, and conveniences 
of expression only. 
It is impossible moreover to restrict the term leaflet to 
‘such growths as arise at an early period in definite order 
upon the wings,’ for in the leaflets of Gleditschia already cited, 
as well as in many other plants, such order is often broken 
through. 
Goebel, speaking of the pitcher-flaps in Nepenthes and 
Sarracenia Y , says, ‘in alien Fallen sind diese Fliigel nach- 
traglich entstandene Wucherungen,’ but such is not the case, 
1 Op. cit. p. 102. 
H h 
