128 LIFE OF A TREE. 
Some flowers are quite exceptions to this rule. 
Thus there is a splendid flower called the 
night-blowing cereus, which is scentless all day, 
but at night bursts into fragrance, and fills the 
conservatory with odour. This remarkable 
flower begins to put forth its delicate scents 
about six or seven in the evening, and continues 
almost literally breathing forth perfume until 
about midnight, when the process ceases, and the 
flower becomes scentless as in the day. Some 
of the Pelargoniums and Orchids have the same 
curious property. ‘These facts only serve to make 
us more puzzled than ever about the source and 
cause of odour in flowers. They shew us, after 
all, how little science knows of the more deli- 
cate and minute points in Natural History ; and 
while they may make us more diligent in pur- 
suing our researches, they should also make us 
more desirous for the arrival of that period when 
“though now we know only in part, we shall 
know even as we are known.” 
The sun is sinking toward the horizon, the 
evening breeze springs up, and whispers the 
leaves of the wood to sleep; high in the clear air 
an army of rooks speeds its straight, undevious 
