34 
natukk .study. 
and heart-shaped or long and narrow ; while the blos.soins 
and seeds present an almost infinite variety. 
We thus begin by learning to know plants, as we do in¬ 
sects, birds and all objects in nature, by their differences. 
Blit we soon observe that two plants which are unlike may 
have one or more things in common. They may have the 
same kind of roots, their stems may be of a similar char¬ 
acter, their leaves may have the same arrangement, or 
their blossoms may be alike in .some essential feature. 
Those plants which po.s.se.ss some feature that is common 
to themselves but which is not found in other plants, are 
said to belong to the same group or family, and they are 
given a family name by which all the different kinds of 
plants that have this common feature are known. Thus 
we learn to know plants finst by their differences and then 
the groups of plants by their resemblances. 
All plants have roots, and nearly all have stems, leaves, 
blossoms and fruit, or something that takes the place of 
them. In the next Nature Study Te.sson we will see what 
we can find out about the roots of such plants as we can 
come b}^ easil}^ We will find out how many kinds there 
are by studying their differences ; and then we will try to 
find out what plants may be placed in groups whose mem¬ 
bers have the same root resemblances. 
Humming in the Air. 
Gilbert White, known the world over as “ The Natural¬ 
ist of Selborne,” frequently heard a humming in the air 
which, close observer as he was, he could never satisfac¬ 
torily explain. Since his time other English naturali.sts 
have made note of a similar phenomenon, and several the¬ 
ories have been advanced in explanation. 
A few months ago, a writer in Nature Notes, the organ 
of the Selborne Society, reported observations which led 
