
Reproduction (seed function). 
THE STEM AL 
Many plants reproduce by 
means of stems (Fig. 5), this being by far the most usual mode 
of vegetative repro- 
duction in flowering 
plants. 
Two of the most 
common methods of 
stem reproduction are 
by rhizomes (stems that 
grow horizontally in 
the soil) and by run- 
ners (stems that grow 
along the surface of 
the soil). Both rhi- 
zomes and runners 
‘may produce roots at 
the nodes. In some 
species the internodes 
do not persist long, 
and each new node 
forms a new plant. In 
other species an in- 
crease in the number 
of plants comes about 
only by the branch- 
ing of rhizomes and 
the ultimate decay of 
the whole of the older 
portion formed _ be- 
fore branching took 
place (Fig. 172). The 
method of reproduc- 



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Fre.171. Section through haustoria and _por- 
tion of host of Cuscuta (see Fig. 170) 
Note that cells of the haustorium are between 
the xylem and the phloém of the host, and that the 
xylem of the parasite is in contact with that of 
the host. (x 70) 
tion by runners, and especially by rhizomes, is well suited to 
increasing the number of plants in a limited area or to the 
invasion of an area next to that in which the parent plants are 
growing. A new plant growing from a rhizome has a much better 
