9 
temperate winters originated in such a species as the Brazil-nut 
(Bertholletia excelsa), it would have practically no opportunity to 
establish itself outside its present tropical range. Under natural 
conditions the seeds of this tree soon lose their viability, tropical 
climates stretch away on each side of its range. Birds, winds, 
waves, and currents could not except in rare cases and for short 
distances act as distributors. Hence its presence would remain 
unknown to man. No members of this family (Lecythidaceae) 
are known in temperate regions. ; 
On the other hand, the Bignoniaceae is well known to be 
eminently an American tropical family. ‘‘The chief glory of 
the American tropics,’ some have called it. Its seeds are 
equipped for both wind and water travel. A cold-resistant 
mutant in this family, even though it originated in the tropics, 
would have a much better chance of reaching a temperate climate 
through wind, birds, or water. It is represented in cool-temper- 
ate climates by the trumpet creeper (Campsts radicans) and 
several species of Catalba. But hundreds of species occur in the 
South American tropics. 
The custard apple family (Anonaceae) is another tropical 
family with a cool-temperate representative, the northern pawpaw 
(A simina triloba), which is hardy in Massachusetts. It too has 
more mobility than the Brazil-nut. 
In a few instances, man has discovered hardiness or ability 
to tolerate low temperatures in plants with a sub-tropical or warm- 
temperate distribution. Such is the case with Leztneria flort- 
danum, with a northern range limit of southern Missouri, yet it 
is perfectly hardy in Massachusetts at the Arnold Arboretum. 
A specimen of Magnolia grandiflora grows in Brooklyn, opposite 
asmall park. Its natural northern range limit is South Carolina 
through middle Georgia and Alabama. This specimen came 
originally from North Carolina. It has withstood over thirty 
winters. According to Rehder (1916), the variety grandiflora of 
Stewartia pentagyna is much hardier than the species, and both 
grow side by side in the woods of Georgia. The species is hardy 
at Poughkeepsie, N. Y., far north of its natural range in North 
Carolina and Tennessee. According to the same authority a 
race of Cedrus libant introduced from the highest altitudes in 
Asia Minor is perfectly hardy at the Arnold Arboretum while 
