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POPULAR SCIENCE REVIEW. 
especially as we know that England and Ireland were formerly 
united witk eack other and with the Continent. 
The second of these modes is not sufficient. For_, although 
we should allow that all the British cryptogams_, mosses^ ferns^ 
&c.^ and some of the phsenogamous plants may have been able 
to cross the seas after the separation of these islands from the 
Continent JQt, after making every allowance for all existing 
means of transport there still remain a number of species of 
animals and plants which it is impossible should have found 
their way to their present stations by any causes now in action. 
The nature of their seed^ and certain bodily characteristics and 
peculiarities in their distribution_, prevent us from entertaining 
such an idea. We are thus driven to the last consideration_, 
migration before isolation/'’ and we must seek for further in- 
formation in geological inquiries. In fach the present state of 
geology and natural history obliges us to regard our flora as 
constituted of plants of a different date and origin. They must 
all be referred to geological epochs more or less ancient. 
The probable great antiquity of all our plants^ under their 
existing forms^ impressively suggests itself from the following 
facts and considerations. 
There are trees now in England whose great age cannot be 
doubted. Oaks, which were planted before the time of the 
JSTorman invasion, and which are therefore more than 800 
years old. The yew-trees {Taxus haccata) are still older. 
One still growing at Fountains Abbey, near Ripon, in York- 
shire, was examined by Pennant in 1770, and was then more 
than 1,200 years old ; and another, in the churchyard of 
Braburn, in Kent, according to the measurement of Evelyn, 
in 1660, had then attained an age of 2,880 years, and conse- 
quently is now more than three thousand years old. Now we 
know from experience that the same specific forms of herba- 
ceous plants have been continued for several generations. 
Apply this to ligneous species, such as the oak and the 
yew, and suppose these old English oaks and yews to have 
been preceded by only twenty generations of the same species, 
— and why should we not ? — and you get for the oak form an 
antiquity of 16,000 years. But if our readers hesitate to accept 
this, then we must remind them of those famous foreign trees, 
the mammoth pines of California and the Baobab of Africa, 
which are known to have been in existence for several thousand 
years. If we limit the number of preceding generations of 
these trees to only four, then the prior existence of the species 
must be immediately dated back 12,000 years for the Califor- 
nia pines, and for the Baobab, which is upwards of 5,000 
years old, 20,000 years ! 
All our cereals, such as wheat, barley, rye, oats, are annuals. 
