THE CONDUCTING SYSTEM. 215 
removed. If sucha root-stock be placed in a liquid prepared 
from decomposed meat, after a short time the parenchyma will 
be destroyed, and, after washing away the remnants of the 
same, the far more resistant threads alone remain behind. These 
do not run parallel in this case, but are variously intertwined 
(Fig. 132). 
In the root-stocks of the Zingiberacew and in Rhizoma 
Caricis there are numerous isolated bundles distributed 
through the fundamental tissue; in Sarsaparilla and in Rhizoma 
Graminis they are brought together in the form of a ring 
(vascular-bundle ring). Differently constructed from these (see 
below), but similar in their entirety, are the vascular bundles 
in dicotyledonous roots, as likewise in the dicotyledonous stem, 
which unite to form a continuous “ring.” Dicotyledonous 
roots often possess only a central, axial bundle (Jpecacuanha, 
Taraxacum, Levisticum, rootlets of Arnica, Valerian, and 
Helieborus ; compare also the Figures 119, 120, 122). 
But we meet these bundlesalso elsewhere onevery hand. The 
fruit-pulp of tamarinds is traversed by such coarse, string-like, 
vascular bundles, and the shell of the almond is covered with 
them. They occur in the arillus of the Myristica (Macis), as well 
as in the mericarps of the Umbellifere, in the calyx of the clove, 
as well as in the stigma of the Croeus—everywhere forming 
long threads, which serve for conveying and for conducting 
away organic and inorganic building material. 
The elements of the vascular bundles are so constructed that the 
impediments to movement are restricted to a minimum. The 
transverse walls are greatly reduced, often lacking altogether at 
wide intervals, or, when present, provided with pores’ (vessels), 
or even pierced with holes (sieve-tubes), thus having the dif- 
fusing surfaces greatly enlarged. 
Of what elements is such a vascular bundle or conducting 
‘The term pores, or pits, is applied to all those thin places of the © 
membrane which are still closed only by the middle lamella. By age 
the pits occasionally become actual perforations (as in the wood of the 
Conifere) ; compare page 153. | 
