ANIMALS AND PLANTS 247 
visits are prevented. In more highly specialized flow- 
ers the parts are usually so modified as to restrict the 
insect visitors to a smaller number; in extreme cases 
often a single species, or a few species belonging to a 
single genus. Thus in the buttercup family we find not 
only the generalized type of flower of Ranunculus, or 
Anemone, but the highly specialized ones of the colum- 
bine (Aquilegia) (Fig. 50), larkspur (Delphinium), and 
monk’s-hood (Aconitum). In these the parts of the 
flower are very much changed, and in the columbine 
and larkspur deep nectaries are developed which are 
accessible only to insects with long tongues, like 
bumblebees or butterflies; or in the case of the scar- 
let-flowered columbines, they are visited by humming- 
birds. It is interesting to note that in these extremely 
specialized Ranunculacee there has been little depart- 
ure in the number of parts from the primitive buttercup, 
and all the parts remain quite separate. 
It sometimes happens that the flowers themselves 
remain inconspicuous, but are grouped together with 
showy colored bracts about the inflorescence, and these 
showy leaves serve to attract insects just as the petals of 
other flowers do. Familiar examples of this are seen in 
the common “calla-lily,” (Fig.55), where the large white 
spathe surrounding the small flowers is very conspicu- 
ous, and many other aroids, such as species of Anthu- 
rium, possess these showy spathes. Another similar 
case is that of certain species of Cornus, like the beau- 
tiful dogwood (C. florida, Fig. 55, B), where the group 
of small flowers is surrounded by four large white 
bracts, the whole looking like a large four-parted flower, 
and the tree when in bloom is exceedingly showy, 
