168 
THE PRINCIPLES OF BOTANY. 
I will now proceed to detail the results of my own observa¬ 
tion, introducing, as occasion requires, such particular statements 
of these several authors as are not mentioned here. First, as to 
the general character and structure, and the arrangement and 
direction of that part of the mistletoe which lies within the 
nourishing plant. 
Its ramifications are composed of a delicate, yellowish-green, 
soft cellular tissue, which, shortly after making sections of a 
branch charged -with mistletoe, shrinks below the level of the 
wood to the same extent as its younger layers of bark. When 
moistened, however, the young roots immediately swell up and 
project considerably above the surface of the wood. 
The young roots, and the equally soft cellular terminations of 
the older ones, are chiefly composed of delicate tubular cells, the 
e~Wth of an inch long and the --oVoth of an inch wide, joined 
end to end, and arranged parallel to each other, and to the long 
axis of the root. 
This parenchyma is pervaded by a few (the number depend¬ 
ing upon the age and size of the root) straggling plates of young 
prosenchyma, each composed of one or two layers of small, thick- 
walled elongated cells, destitute of markings. 
Arranged in the same radiate manner as the plates of prosen¬ 
chyma, and in the larger roots associated with it, but in the 
younger occurring alone, are narrow bundles of vessels formed of 
one, two, or three rows of very delicate reticulated ducts com¬ 
posed of elongated cells -^Wth of an inch long, and T i ? th of an 
inch wide, joined to each other by their oblique ends. The 
woody fibres and ducts take the same direction as the root. 
The extremities of the young roots, the base of the mistletoe, 
gradually diminishes in size from the surface of the supporting- 
branch inwards, that being the thickest part of the entire plant, 
which corresponds in position to the outer surface of the last 
formed layer of the wood. From this situation the base of the 
parasite in its simplest condition, tapers as it passes towards the 
centre of the branch—gradually in the case of a young plant, 
so as to form a long, tapering root, suddenly in an old plant— 
forming a short, conical, woody plug, which, however, invariably 
ends in a slender cellular process. But more commonly the base 
of the mistletoe terminates in three or four, and sometimes 
five or six such tapering roots, when the base of the parasite 
does not exceed at its thickest parts -jVths of an inch in diameter 
itself, and all are altogether destitute of prosenchyma, but here 
the ducts are very numerous. The parenchymatous cells which 
form the surface of the root, and connect it with the tissues of 
the nourishing plant, are narrower than those lying more inter¬ 
nally, and measure only the Vo~oth of an inch wide. A similar 
