108 PLANT STRUCTURES 
Bird’s-nest (Neottia Nidus-avis), which does not 
produce leaves or chlorophyll, but sends up from its 
fungus-infested roots merely a scaly brown stem 
topped with brown blossoms, matching curiously the 
dead leaves among which it grows (Fig. 31, p. 182). 
In contrast to these the case of certain other 
Orchids may be quoted, which have also lost their 
leaves, but in a very different manner. In their case 
the roots, creeping over the bark of trees on which 
the plants perch as epiphytes, have become green and 
flattened, like the fronds of some of our native Liver- 
worts; they have assumed the functions of leaves: in 
them the process of photosynthesis is carried on; 
and the leaves themselves, thus supplanted, have by 
degrees disappeared. 
Like many other parts of plants, roots are often 
used for the storage of reserve supplies of food or of 
water. For this purpose they become much thickened, 
and this thickening is*the most conspicuous change 
which roots usually undergo. Note the fat roots of 
many plants which grow in dry or arid places, such as 
the Sea Holly, Dandelion, and many desert plants and 
alpines. The thickening is often accompanied by 
increase in length, as the roots range far in search 
of water. Another point to notice is that though 
normally roots differ considerably from their asso- 
ciated stems in general appearance, and also in their 
minute structure, as in the arrangement of the vascular 
strands, the two are related. Stem structures are often 
produced at various points on roots; the suckers sent 
up by many kinds of trees offer an example. Con- 
versely, roots are readily produced even from the 
upper portions of many stems—else how could we 
