Bogdan wrote:
Hello!

I'm trying to find out how could I determine the exact (as far as
possible) species of a few trees I found in my University's campus.
(And, more generally, how to find out the species of any tree in
general.)

I'm pretty much a noob on the subject. I have the basic knowledge of
high-school biology, and I have access to Wikipedia and I'm not afraid
to use it. I can learn whatever is needed, but I have no idea where to
start.

I assume there must be something like a "dictionary" somewhere, where
I can search for traits and find the matching species. I looked around
on the net but found only small boy-scout-type "know the trees in your
area" info. But my trees are in France, and besides, I have no idea if
those particular trees are "native" or not.

I have access to the trees, so I can examine how they look. The
leaves, bark and fruit should be easy to describe. However, this being
France, they have probably been pruned extensively, so I'm not sure if
the general shape of the trunk and branches is natural.

In case there is no "universal dictionary", maybe someone can point me
in a more restricted direction:

One of the trees is some kind of chestnut according to the fruits;
it's probably quite old, the trunk is more than a meter in diameter.
It's weird in that the low part (up to knee-height) is wider than the
rest of the trunk by almost a half, and very gnarly; I suppose it's
because of early pruning; the crown is more wide than tall. The other
trees in the area don't look like that, even if the fruit seem
identical at first look.

The other tree is strange (to me) because it has spiny leaves like
those of conifers, but it has small (0.5cm) cylindrical red fruits
with a single seed inside.

Thanks for any pointers.
In addition to BAE's good advice, if the university has a botany or
horticulture department, there's likely a professor (or more than one)
who happen to know virtually all of the plants on the campus. If you
can locate that person, and if he/she has the personality to enjoy such
a challenge, they may take you out on a campus hike, identifying plants
as you go. We do that all the time on our campus, when we can spare the
time -- it's a great educational experience. If they don't have time
for that, either such department ought at least to be able to tell you
the appropriate key(s) to be looking for.

Malcolm Manners
Horticulture
Florida Southern College