196 DR. HARLEY ON THE PARASITISM OF THE MISTLETOE. 
Fig. 10. Transverse section of a branch of Crab (Pyrus malus), bearing Viscum album (c). The hyper- 
trophy of that side of the branch upon which the Mistletoe is situated is well shown. 
Fig. 11. Transverse section of a branch of Hawthorn, and longitudinal section of the roots of Viscum 
album contained in it. "Their convergence, the opening out of the woody layers towards the 
roots of the Mistletoe, and the transverse rhizomata and their effect in destroying the bark 
and arresting the development of the wood are seen in this section. 
Fig. 12. Longitudinal section of Populus nigra, bearing Viscum album. The nipple-shaped processes 
towards the wood are the oblique sections of the cellular roots in which the base of the para- 
site terminates. The branch is atrophied and dead above (a). 
PLATE XXX. 
Fig. 13. Section of the wood of Maple (Acer campestre) and of five young roots of the Mistletoe per- 
forating it, taken at the distance of about 14 inch beneath the bark (x54). The tissues of 
the wood are divergent around the roots, and are otherwise much distorted by their proximity. 
Each root appears to be enlarging itself by absorbing and distending the tissues around it. 
Towards a, two of these roots have become confluent. 
Fig. 14. Section of wood of Maple and a young root of Viscum album, made at right angles to the 
medullary rays ( x 60) : a, a, medullary rays of Maple; 5, b, pitted ducts diverging with the 
woody fibres around the root. Contiguous to the lower part of the root the tissues of the 
wood are partly absorbed, and at several parts of its circumference the medullary rays are 
seen to be confluent with the root. c, radiating plates of prosenchyma and slitted vessels: 
the latter become larger and more delicately reticulated externally, and form the reticulated 
ducts. Some of the parenchymatous tissue between the young woody plates is not represented. 
Fig. 15. Upper part of fig. 14, x 250: a, a, medullary rays; 5, pitted ducts of Maple; c, reticulated 
ducts of Viscum, cut across. 
Fig. 16. Wood of Maple, and Viscum-root, seen in oblique section: a, a, a, medullary rays of Maple; 
6, wood-fibres and ducts of Maple; c, cells composing Viscum-root. 
Fig. 17. Section of wood of Maple and cellular root of Viscum, at right angles to the woody fibres and 
: ducts of the former, and horizontally parallel with the long axis of the latter, x 250: 
a, woody fibres and ducts of Maple cut across; 5, parenchymatous cells and reticulated ducts 
of Viscum-root, the long axes of both at right angles to the prosenchymatous cells and ducts 
of Maple. 
Fig. 18. Vertical section of Populus nigra and Viscum album ( x 100), taken from the surface and made 
at right angles to the medullary rays: a, a, a, reticulated ducts of Viscum, between which lies 
the parenchymatous tissue composing the hypertrophied medullary rays (the ducts at their 
junction with Populus are cut across); b, b, pitted ducts of Populus, with medullary rays and 
wood-fibres intervening. 
Fig. 19. Transverse section of the coincident woody layers of the same: a, a, thin-walled parenchymatous 
cells of medullary rays; 5, رق‎ thick-walled dotted cells of the same; c, reticulated ducts of 
Viscum, seen first in oblique section, and then at their junction with Populus in longitudinal 
section; d, d, medullary rays of Populus parallel with those (a, b) of Viscum; c, ducts of 
: Populus cut across obliquely, as are the woody fibres also. 
Fig. 20. Vertical section of Crategus oryacantha and woody base of Viscum album, taken from the surface 
and at right angles to the medullary rays: a, ducts of Viscum, with medullary rays in trans- 
verse section intervening; 5, medullary rays of Crategus, in transverse section, with ducts 
and fibres intervening. The ducts of Viscum are cut across at their junction with Craíegus. 
All the figures, except 13, 14, 15, 16, 17, 18, 19, & 20, are of natural size, and were taken while the 
specimens were moist with sap. 
