THE STEM | 165 
SPECIALIZED STEMS 
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The chief function of ordinary stems is to support the leaves 
and reproductive organs in such a way that they can carry on 
their several functions advantageously. Many stems, however, 
are specialized for functions which are unusual for stems, or are 
fitted to perform the usual functions in a somewhat specialized 
manner. Stems of these 
types may be called spe- 
clalized stems. They 
may be divided into 
the following general 
classes: unusual meth- 
ods of support (stem 
function), photosynthe- 
sis (leaf function), ab- 
sorption (root function), 
reproduction (seed fune- 
tion), storage, and pro- 
tection. ‘This list is very 
similar to that given 
for specialized leaves. 
Frequently the only 
_ way in which we can 
tell by superficial eX- Fic. 162. Stems modified as hooks 
aminati heth 
2 ation whet eo " Above, Artabotrys uncinatus ; below, Uncaria 
given structure 1s a gambier. (x 2) 
stem or a leaf is by 
the mode of its attachment. If the structure is in the axil of 
a leaf, we regard it as a stem, while if a stem or bud is found 
in its axil, it is considered a leaf. 
Unusual methods of support (stem function). Stems that are 
specialized in no other way than to support the leaves and re- 
productive organs in a rather unusual manner are well exem- 
plified in climbing plants. The chief advantage of the climbing 
habit seems to be that it enables a plant to reach up into the 

