164 
Transactions of the 
[Monthly Microscopical 
Journal, March 1, 1869. 
appear to me to be at length capable of solution. In order to show 
this, however, it will become necessary to dispense with certain pre- 
conceived notions as to the structure of the lobed leaf: to consider 
it no longer as a single blade, from the margin of which certain 
portions of determinate outline have been cut or excised, and through 
the substance of which the veins proceed in a deviating, often unde- 
termined course ; but rather as a structure consisting of many 
similar parts, quasi leaves, the number of which is indicated by that 
of the lobes, and the junction of which has converted what would 
otherwise have been a compound, into a simple lobed leaf. That 
such union of the leaflets is actually effected, has been partially dis- 
cussed ; but we think it can be proved, almost to demonstration, by 
cumulative evidence from a variety of sources, viz. — (1) hy direct 
a^ppeal to the leaf itself; (2) hy synthesis; (3) hy analysis; (4) hy 
metamorphosis ; (5) hy analogy, 
(1). Let us take any well-defined lobed leaf — say that of Syca- 
more — and map it out into regions, which are suggested by a 
careful inspection of its integral parts. 
EXPLANATION OF THE DIAGKAM, 0, PLATE V. 
L C X, Intercostal space, or space bounded by two adjacent costsB, and con- 
taining : — 
S C, Commissural space, in which the vessels from two adjacent leaflets anasto- 
mose. 
LAS, Lobular space, in which the vessels of the typical leaflets are not altered 
by anastomosis. 
OHM, Lobular space on outer half of the lowest costse, 0 M, in which the vessels 
of the typical leaflet are unaltered by anastomosis. 
L S ^L, Interlobular space, broad and deep, or narrow and shallow, varying with the 
angle of the costse (L 0 L) and the breadth or expansion of the typical leaflet, 
LSO. 
L, Apex of lobe. 
S, Sinus between two lobes ; the part where the lobes commence, or where the 
coalescence of two typical leaflets ceases. 
L S, and 0 H M, Edges of typical leaflets, which retain their primitive outline 
unaltered by coalescence. 
According to this showing, it would appear that the leaf in 
question is composed of five distinct feather-veined leaflets ; that these 
leaflets are all united in those regions indicated by actual inspection 
of the leaf, and defined (C S) in the diagram ; that the venation in 
each of the leaflets is nearly that of a perfect feather-veined leaf, and 
that its normal type is clearly visible in those parts, LAS and 
C H M, where the vessels could not by possibility anastomose ; but 
that the venation becomes mixed — abnormal — in those regions, C S, 
where the vessels must meet, and where anastomosis is inevitable. 
It is evident also that the free projections of leaf texture beyond the 
sinus S, and called lobes, are really the terminations of the leaflets 
themselves, being veined, and notched or toothed at their margins 
like ordinary leaves ; again, that the recesses between these lobes are 
