ROOTS AND THEIR RELATION TO PLANTS 29 
Fic. 20. A desert Pelargonium 
(closely related to the common so- 
called geraniums) 
Note the scanty leaf surface and the 
fleshy root and base of the stem, con- 
taining much water and reserve food. 
After Andrews 
rainfalls of the regions where 
these plants grow. Others, as 
the mesquite of the extreme 
southwest, have roots that pen- 
etrate into the earth to extra- 
ordinary depths until they reach 
moist soil. Still others — for 
example, many South African 
plants (fig. 20), some wild 
morning-glories, and the big- 
root’ of the Pacific coast — 
have fleshy roots in which much 
water is stored. 
28. Water roots. Most aquatic 
perennials, like the cat-tails, ar- 
rowheads, pickerel weeds, pond 
lilies, and many grasses and 
sedges, form mainly earth roots. 
On the other hand, some plants 
not aquatics —for example, many willows—can develop roots 
indifferently either 
in earth or in water. 
Willows growing 
along a brook usu- 
ally send great 
numbers of roots 
into the earth, and 
also produce a mul- 
titude of fibrous 
roots which dangle 
in the water. Cut- 
tings of Wander- 
ing Jew (Zebrina), 
geranium (Pelargo- 
nium), and many 
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Fic. 21. Duckweed, a floating aquatic plant 
At left, top view of single plant 8 times natural size ; 
at right, group of three individuals of another species 
represented as floating, with roots hanging vertically. 
Three and one-half times natural size. After Prantl 
1 Echinocystis. 
