80 PRACTICAL FORESTRY 
vigorous neighbors, or fall an easy prey to insect and 
fungus pests, which would relish a new food material; 
but by a slow process of acclimatization and fostering 
care, however, even our northernmost species might 
in time become accustomed to the new environment. 
Northern annuals would become perennial, northern 
light-demanders would become shade-demanders, and 
northern slow-growers might become rapid-growers 
under the favorable conditions of a southern cli- 
mate. 
In the tropics there are many palms which have 
no representatives in northern regions. The common- 
est grasses, such as bamboo, grow to be trees. The 
same is true of ferns. . 
Slow-growing and rapid-growing are only com- 
parative terms. Theze are slow-growers and. fast- 
growers in the tropics as in northern regions. There 
are many heavy slow-growing hardwoods in the trop- 
ics, but, as a rule, in consequence of the abundance 
of warmth, moisture, and fertile soil, growth is very 
rapid. Although the highest mean temperature for 
the year is found in the torrid zone, the maximum 
readings of the thermometer are obtained at about 
the thirtieth parallel of latitude during the summer. 
It is also in about that region, which is in the neigh- 
borhood of New Orleans and St. Augustine, that frost 
often causes very serious damage. It is about here, 
