ROOTS 33 
primary roots, that is, a cluster proceeding from the lower 
end of the hypocotyl at the outset. If such roots become 
thickened, like those of the sweet potato and the dahlia 
(Fig. 17), they are known as fascicled roots. 
Fic. 14. Dodder growing upon a Golden-Rod Stem. 
s, seedling dodder plants, growing in earth; h, stem of host; 7, haustoria 
or parasitic roots of dodder; /, scale-like leaves; 4, magnified section 
of a portion of willow stem, showing penetration of haustoria. 
