296 Science of Plant Life 



the formation of resin is not known. Resin is a valuable 

 commercial product, and in the Southern states the long- 

 leaf pine furnishes the crude rosin and the turpentine of 

 commerce. 



Leaves of conifers. The leaves of most conifers are ever- 

 green and remain on the trees for a period of from 2 to 10 

 years, depending somewhat upon climatic conditions. In 

 general they last longer in moist habitats. The Northern 

 larch or tamarack and the Southern cypress are deciduous 

 trees with soft needle leaves that contrast strongly with the 

 hard needle leaves of the evergreens ; the hardness of the 

 evergreen needles makes it possible for them to withstand the 

 winter droughts. 



Roots of conifers. The roots of conifers are far better 

 developed than are those of the ferns. Like deciduous trees, 

 they have root systems that gradually taper from the stem 

 base and spread over a wide area. The great root system 

 makes possible the development of a large crown and the 

 exposure of a greater leaf surface than in the ferns. 



Production of seeds. The production of seeds in conifers 

 may be illustrated by the pine. Two kinds of cones are pro- 

 duced : the stamina te cones that produce the pollen, and the 

 ovulate cones that bear the seeds (Fig. 175). The staminate 

 cones are short-lived structures of early spring. Each scale 

 bears two pollen sacs, which contain the pollen grains. The 

 pollen is blown about by the wind, and each grain has on its 

 sides two little air sacs that cause it to be carried through 

 the air easily. It is produced in enormous quantities ; and 

 when it is shed, it oftentimes colors the ground yellow in the 

 vicinity of pine woods. The staminate cone of the conifers 

 corresponds to a staminate flower in the flowering plants ; 



