i 
SIZE OF DICOTYLEDONOUS TREES. 87 
that some trees were estimated by De Candolle to be more than 
5,000 years of age, we cannot but believe that such calculations 
give an exaggerated result. But, however erroneous they may 
have been, still there can be no doubt but that Dicotyledonous 
trees do live to a great age ; in fact, when we consider that the 
new rings of wood are developed from the cambium cells which 
are placed on the outside of the previous rings, and that it is in 
these new annual rings that all the active functions of the plant 
are carried on, there can be, under ordinary circumstances, no real 
limit to their age. Mohl believes that there is a limit to the age 
of all such trees, arising from the increasing difficulty of convey- 
ing the proper amount of nourishment to the growing point, as 
the stem elongates from year to year. We cannot, however, 
attach much importance to this opinion, because some trees, as 
the Sequoia (Wellingtonia) gigantea, exist in California as much 
as 450 feet in height, and species of Hucalyptus may also be 
found in Australia which have reached nearly or quite the same 
height. 
The following table is given by Lindley of the age of some 
trees, all of which, he states, can be proved historically :— 
An Ivy near Montpellier . ‘ : . 433 years. 
Lime trees near Freiburg . ‘ . . 1230 
», Neustadt . : f OU) 
Larch : ‘ ‘ . 5976 
Cedars, on Mount Lebanon , . 600—800 
Oaks . ; , ‘ : . at least 1000 
There can be no doubt, therefore, but that such trees will 
live beyond the above periods. Other trees, such as the 
Sequoia, Yew, and Olive, may be added to the above list ; thus, 
it is probable that the former will live at least 3,000 years ; and 
it seems certain that the Yew will attain the age of 1,200 years, 
and the Olive at least 800 years. 
Size of Dicotyledonous Trees.—As there is no assignable limit 
to the age of Dicotyledonous trees in consequence of their mode 
of growth, so in hike manner the same circumstance leads, in 
many cases, to their attaining a great size. Thus the Sequoia 
gigantea has been measured 116 feet in circumference at the 
base ; the Chestnut tree (Castanea vesca) of Mount Etna is 180 
feet in circumference ; ; a Plane tree (Platanus orientalis) near 
Constantinople is 150 feet in circumference ; the Ceiba tree 
(Bombax pentandrum) is said to be sometimes so large that it 
takes fifteen men with their arms extended to embrace it ; even 
Oaks in this country have been known to measure more than 
50 feet in circumference ; and many other remarkable examples 
might be given of such trees attaining to an enormous size, 
which circumstance is of itself also an evidence of their great age. 
4. Cambium-layer or Cambium (figs. 179, ¢, and 185, A, and B, 
e).—On the outside of each annual ring of wood, aswe havealready 
