74 PRACTICAL FORESTRY 
more importance. We should be much more inter- 
ested in knowing where trees will grow, than where 
they have grown. 
1. Arps to Forrest Extension 
Seeds are often provided with attachments to aid 
in their dissemination. Some seeds have wings by 
means of which they are blown long distances by the 
wind, such as those of the spruce and pine, which 
whirl in a circle as they fall to the ground. In that 
way their fall is retarded, so that the chances of their 
dissemination by the wind are greatly increased. The 
seeds of the basswood, or linden, are borne on the 
midrib of the leaf, which falls with the seeds, and 
acts as a kite in aiding their distribution. Some seeds 
are formed within little bladders, as with the hop- 
hornbeam. The bulk is large in proportion to its 
weight, so that transportation by the wind is facili- 
tated. 
Birches and poplars often appear on burnt-over 
land far away from the mother-tree. This is due to 
the ease with which their light-winged seeds are car- 
ried long distances by the wind. 
Other seeds are covered with a pulp which, when 
ripe, is edible. In the center there are usually one 
or more hard seeds which resist the action of the 
digestive juices and pass through the animal unin- 
