516 PRINCIPLES OF BOTANY, ETC. 
the consequence. And every insect that even doeg 
not visit one sort of flower alone, but many indiscri- 
minately, will, during a whole day, remain with that 
species on which it first fixed in the morning, and 
not touch another, provided there be enough of the 
first species. ; 
Those flowers alone which secrete a sweet juice, 
are visted by insects. Several of these flowers have - 
one or more coloured spots, which Mr Sprengel 
calls Maculae indicantes, as they always indicate that 
a plant possesses honey, and, as he believes, make 
the insect more attentive. In hairy flowers the hair 
is always placed so as to prevent the rain from drop- 
ping in, and not to allow the insect to enter the 
flower at any place whatever, on purpose that it 
may be obliged to make its way across the stamens. 
The filiform and leaf-like appendages, which we 
enumerated amongst the parts of flowers, (§ 84), 
and which defend the honey, serve the same purpose. 
But it would be needless to give a more detailed 
account of the manner in which insects do this, as 
we can see it better with our own eyes, if the least 
acquainted with the structure of flowers. If we 
only look at the Iris germanica, at many flowers of 
the class Didynamia, at the Symphytum officinale, 
and many other plants, we will soon find ample 
satisfaction. One of the most singular ways of 
the fecundation of plants through insects, we have 
in the Aristolochia Clematitis. Fig. 271 represents 
this flower on a small scale; it has a linguiform 
corol, which at its inferior part is spherical, to- 
wards the top it becomes long and tubular, and its 
4 margins, — 
