Chap. III.— B. S.J MIMICRY IN NATURE. 47 
I met several curious instances of this; some plants 
belonging to what Humboldt has aptly termed the 
willow form. There were genuine willows, which the 
country-people termed “Sauce,” the fresh green of 
which afforded a pleasing relief to the eye after gazing 
so long on dried-up or leafless vegetation; hut with 
them grew not only the feathery bamboo, and the beau¬ 
tiful Lindenia rivalis (both good instances of the willow 
form), hut also a yellow-flowering Bignoniacea (. Astian- 
thus longifolius , D. Don), often forty feet high, and a 
tall Composite/,, the latter two both known by the 
Quichuan name of “ Chilca.” All these plants, un¬ 
affected by the periodical rising of the water and the 
turbulence of the stream, not only had the same 
foliage, habit, and mode of growth, as genuine wil¬ 
lows have, hut served the same purposes in nature’s 
economy, viz. protecting and keeping together the river 
hanks. In the Yiti Islands* and many other parts 
of the world I observed similar instances of the pre¬ 
dominance of the willow form on rivers; the question 
then as now naturally presented itself,—what possible 
connection can there he between the two ? Do these 
plants grow on rivers because they have willow-leaves, 
or do they have willow-leaves because they grow on 
rivers ? This is, in fact, the old question over again— 
Does the duck swim because it has webbed feet, or has 
it webbed feet, because it swims ? 
Having purchased mules, hammocks, provisions, 
* The plants I observed in Yiti were Lindenia Vitiensis, Acalypha 
rivularis, Ficus bambusafolia, two species of Bamboos,—all belonging 
to different Natural Orders, yet all having willow-leaves. 
