10 DR. J. D. HOOKER ON THE STRUCTURE AND 
posed of elongated cells which are more opaque towards the centre of the bundle; lower 
down in the peduncle they present the same appearance as is represented in figs. 26 and 27 f 
which show vessels from the apices of the bundles in the rhizome. In fig. 22 some vessels 
of the rhizome, and on the left the base of one of those of the peduncle, are seen : at this 
part of their course both are regularly banded; which is better seen in figs. 23 and 24, 
where they are more highly magnified. Every intermediate form of vessel may be found 
between those represented at figs. 15 and 27; and occasionally in both organs the form 
of cellular tissue, seen at fig. 25, is found; which appears to be another modification; 
intermediate between the vascular and cellular, and which, in fig. 23, is placed outsidé 
the barred vessels. | "n; 
In older specimens of B. involucrata much larger cylindrical vessels are found in thé 
rhizome, mixed with hexagonal tubes with barred or otherwise marked sides, and bundles 
of pleurenchyma, which also occur in the peduncle, but in a much less perfectly deve- 
 loped state. 
I find considerable uniformity in the microscopical character of the vessels amongst 
different specimens of B. dioica, although these have grown on widely different genera of l 
plants (and the same remark applies to Rhopalocnemis) ; and I do not in any case find å 
more highly developed tissue in the peduncle than in the rhizome. Ona comparison of : 
my dissections of young specimens of B. involuerata with Gæppert's of old ones af 1 
B. elongata, the differences between them are perfectly reconcilable. Gceppert figures 
barred cylindrical vessels of cellular tissue as occurring only in the peduncle, and larger 
vessels with short transverse bars as occurring only in the rhizome; this I also find to be _ 
the case in old specimens ; but in younger ones the barred cylindrical vessels are abundant - 
in the rhizome, and comparatively rare in the peduncle; from which it may be inferred; 
that the said vessels are an imperfectly developed tissue. 
In full-grown specimens of B. fungosa (Plate VIII. fig. 12), the same forms, relations, 4 
and modifications of vascular tissue prevail to a considerable extent; and the same may |. 
be said of other species which I have examined, though less in detail; whence I conclude 
that the anatomical differences between the vessels of the rhizome and those of the peduncle 
are dependent on position and degree of development. i 
The rhizome of the most perfect species of Balanophoreæ is decidedly exogenous. Ifa 
transverse section of the elongated one of Helosis mexicana be taken, the mass will be 
found to be composed of cellular tissue, enclosing (in the specimen given at Plate XV. 
fig. 14) a vascular system consisting of seven wedges, which surround a narrow cylindrical 
axis. Each of these wedges is (on a transverse section) narrow and oblong, and consists 
_of many rows of annulate or transversely barred cylindrical or angular ducts, which 
occupy the position of the pleurenchyma of ordinary exogenous plants; outside of these is 
a reniform mass of stout, elongated liber-cells, into whose concave faces the outer ends of 
. the wedges are thrust. Beyond the vascular system is a very thick spongy cellular mass 
are smaller and denser: this cellular 
asses of thick-walled sclerogen-cells, round 
which the cells of parenchyma radiate, and which, in a transverse section, resemble scat- 
å seven-lobed zone of stout sclerogen-tubes, 
él oc L 
