PLANT STUDIES 
FIG. 64. An araucarian pine, showing the 
central shaft, and the regular clusters of 
branches spreading in every direction and 
bearing numerous small leaves. The low- 
ermost branches extend downwards and 
are the largest, while those above become 
more horizontal and smaller. These dif- 
ferences in the size and direction of the 
branches secure the largest light expo- 
sure. 
are of this character ; 
and as the main pur- 
pose is food storage 
the most favorable 
position is a subter- 
ranean one (see Fig. 
66). Sometimes such 
scale leaves become 
very broad and not 
merely overlap but en- 
wrap one another, as 
in the case of the 
onion. 
51. The tuber type. 
The ordinary potato 
may be taken as an il- 
lustration (see Fig. 
67). The minute scale 
leaves, to be found at 
the "eyes" of the 
potato, do not overlap, 
which means that the 
stem joints are farther 
apart than in the bud 
type. The whole form 
of the stem results 
from its use as a place 
of food storage, and 
hence such stems are 
generally subterra- 
nean. Food storage, 
subterranean position, 
and reduced scale 
leaves are facts which 
seem to follow each 
other naturally. 
