168 
Transactions of the 
[Monthly Microscopical 
Journal, March, 1, 1869. 
found in lobed leaves — a normal venation belonging to the leaflets 
of wbich they are composed, and a mixed or irregular venation in 
those parts where they appear to be united by anastomosis. 
13. That when a lobed leaf is examined for the purpose of 
tracing out its integral parts, it may be mapped out into boundaries, 
which contain — (1) structures like little leaves (typical leaflets); 
(2) the edges of such structures joined by the anastomosis of their 
vessels ; and these structures, in their relative size, shape, venation, 
and symmetrical arrangement on the petiole, will be found to 
resemble the leaflets in compound leaves, only united at their edges. 
14. That while the possibility of such junction of leaflets into 
one entire blade is inferred from metamorphosed leaves, it may also 
be presumed to be likely, from analogy with other vegetable struc- 
tures (the union of the edges of a single leaf into a carpel, the 
coalescence of carpels into a pistil, the repetition of similar leaves 
on a branch, and of like branches on a tree), and from a careful 
inspection of lobed leaves themselves. 
15. That the lobes themselves, in simple lobed leaves, are sug- 
gestive of their composite character.* 
16. Assuming that lobed leaves are a multiple of typical leaflets, 
united at their edges into one leaf, it may be inferred : — 
17. That the lobes themselves, in simple lobed leaves, are the 
projections of perfectly-formed typical leaflets, of which the entire 
leaf is composed ; and that these projections are merely the parts of 
such leaflets which have not contracted adhesion to one another at 
their edges. 
18. That the fissures or recesses between the lobes are the void 
spaces between the free margins of typical leaflets. 
19. That the outline of the sides of the recesses is in conformity 
with that of the typical leaflets, while their depth and width is 
directly related to the angle of divergence of the costae of the typical 
leaflets, and to the breadth of the leaflets themselves. 
20. That these spaces are not really the result of splits, fissures, 
or divisions taking place in a leaf otherwise entire ; and hence that 
the terms usually employed to designate such vacancies fail in con- 
veying to the mind their true nature, by assuming the leaf to have 
been once entire, else how could it have suflered excision ? 
21. Hence that the notion of the existence of lobes and openings 
in a leaf, as produced by an imperfect union of parenchyma, and from 
a diminished extension of cellular tissue in the recesses, is untenable. f 
* " Lobed leaves may be assumed as simple leaves approaching composition." 
— LiNDLEY, ' Introd. Bot.,' p. 90. 
t " But when the separation of the principal veins is greater, and the cellular 
tissue is comparatively less extended, the union of parenchyma takes place only 
in an imperfect manner, and thus lobes and openings are produced in the middle 
of the leaf, or various kinds of toothings in its circumference." — De Candolle, 
quoted by Lindley, ' Introd, Bot.,' p. 112. 
