SPECIALIZED STEMS 
263 
stems of plants to be of great use to him, and that he could 
not well do without them. 
229. Adaptations of Wood. — When we compare the number 
of articles that are made of wood with the same articles made 
of substitutes, we see that there are some good reasons for the 
use of wood. Among these are its lightness compared with 
iron or steel for use in furniture, trunks, and other articles, 
its elasticity , its toughness, its durability, especially when pro¬ 
tected from dampness, the ease with which it can be shaped 
by tools, and its beauty, depending on color and grain, and 
on the high polish it can take. 
230. Specialized Stems. — In regions where the climate is 
very hot and dry most of the year, the leaf surface is greatly 
reduced to prevent undue 
evaporation. In this case 
the stem becomes green 
and performs the work of 
photosynthesis (see page 
278), ordinarily done by 
leaves. The cactus illus¬ 
trates this. Certain other 
plants have no leaves but 
the stem branches in such 
a way as to resemble 
leaves. The florist’s smilax and asparagus fern represent this 
kind of branching. The true leaves are reduced to minute 
scales. 
LABORATORY STUDY OF STEMS 
Draw a potato. Label the “eyes” buds. On which end are they 
more numerous? Label scale, just above bud. Note end where it 
was attached to the main plant. 
Cut off the stem end and stand in water colored with red ink. After 
two hours examine again and note what part is stained. Cut off slices 
till traces of color disappear. Draw to show where it is colored- Cut 
a thin slice and put a few drops of weak iodine on it. What happens? 
What does it show? 
Figure 251. — “ Stemless ” Plant — 
Dandelion. 
