8G FLOWERS. 
other of these methods of displaying their blossoms. 
There is, however, a very interesting exception to this 
in the common Dogwood. The 
flowers, which are quite small, 
are clustered in close heads, and 
each head is surrounded by four 
large white leaves, which are 
called an involucre. These leaves 
being very prominent and showy, 
are often mistaken for the flower, 
ae anieesbaiannarns while they only act as appen- 
dages; but they undoubtedly 
have some use assigned them; perhaps it may be 
to protect the delicate little blossoms from the cold 
night-winds which are apt to prevail in the early 
Spring, while they are in bloom. 
Most flowers require the action 
of light to cause them to expand, 
and many never open except un- 
der the influence of the most bril- 
liant sunshine. But there are a 
few instances in which the con- 
trary is observed. Far down in 
the evergreen forests of South 
Fascicle, Sweet William. America, when the sun has set 
behind the tall groves of Palm 
and Mimosa, and the glimmering twilight is fast fol- 
lowing in its train, the magnificent flowers of the 
Night-blooming Cereus may be seen just opening their 
fair petals to catch the first rays of the full-orbed 
moon. ‘Travellers in the tropics describe it as a sight 
