ROOTS. 29 
strength of the supplies of ready-made sap which it obtains 
from the host. 
43. forms of Roots. — 
The primary root is that 
which proceeds like a 
downward prolongation 
directly from the lower 
end of the caulicle. In 
many cases the mature 
root-system of the plant 
contains one main portion 
much larger than any of 
its branches. This is 
called a taproot, Fig. 16. 
Such a root, if much 
thickened and fleshy, 
would assume the form 
shown in the carrot, pars- 
nip, beet, turnip, salsify, 
or radish. Some plants 
produce multiple primary 
roots, a cluster proceeding 
from the lower end of the 
caulicle at the outset. 
Roots of grasses, etc., 
are thread-like,and known 
as fibrous roots, Fig. 17. 
If such roots become thick- 
ened like those of the 
dahha, Fig. 18, they are 
known as fascicled roots. 
These often closely re- 
semble tubers, but they 
Fig. 15.— Dodder (a European species) Parasi- 
tic on the Willow. 
The plant is seen encircling a willow twig, into 
which it sends roots from the warty inner 
surface of its coils. 
b, seale-like leaves ; B/, flower-cluster. 
At the left is shown the manner in which the 
parasite Cus encircles the host-plant W. 
The parasitic roots or haustoria H penetrate 
into the parenchyma of the bark and into 
the fibro-vascular bundles, attaching them- 
selves to the various kinds of tissue, v, c, s, 
which they find in these. 
At the right are seedling dodder plants, the 
longest one growing at the tip from nourish- 
ment which it procures from the dying end 
next the root. 
may be distinguished from them by their mode of origin, 
