502 



NATURE 



{April z, 1879 



whole surface of the earth into a boundless flower- 

 garden," supplying insects from year to year with pollen 

 or honey, and itself gaining in return a renewal of life by 

 means of the baits that it offers for their allurement. 

 " If," adds Mr. Allen, " any man can seriously doubt that 

 these changes are really due to a colour sense in the little 

 creatures which live upon the beautiful flowers ; if he can 

 imagine that the plant has produced its gorgeous petals 

 for no other purpose than that of suicidal wastefulness ; 

 that the Mantis has grown into the perfect semblance of 

 a leaf from pure wanton causeless mimicry ; that thf^ 

 lurid red of fly-fertihsed blossoms bears its likeness to the 

 mangled flesh of animals by a simple freak of creative 

 power ; then the whole science and philosophy of the last 

 hundred years have been thrown away upon him, and he 

 may return at leisure to the blind and hopeless chance of 

 the eighteenth century atheists." 



The relation of birds and mammals to fruits is next dis- 

 cussed, and this is shown to be in many respects parallel to 

 that of insects and flowers, only those fruits being conspicu- 

 ously coloured which are edible, and the dispersal of whose 

 seeds is effected by the birds or other animals which eat 

 them. The whole of this subject is very well treated, 

 but the evidence that fruits in general have been modified 

 both in edibility and attractiveness in relation to the 

 animals which feed upon them, is by no means so clear 

 as in the case of flowers. With regard to small and hard- 

 seeded, fruits, such as our strawberries, currants, and 

 raspberries, our hips and haws, our yews and cranberries, 

 this is no doubt the case, since they are carried away by 

 birds and vegetate after passing through their bodies. It 

 is also the case with such fruits as the nutmeg, whose 

 bulky seeds pass undigested through the stomachs of the 

 great fruit pigeons, but whether the same rule applies to 

 most of the larger fruits may be doubted except when 

 they have hard, stony seed-coverings, as in the case of 

 plums and apricots, which evidently protect the seeds 

 from being eaten, or, if eaten, from being digested. But 

 the majority of the larger fruits are eaten by mammals, 

 and it is doubtful whether their seeds can survive the 

 process. Such are oranges and shaddocks, and gourds of 

 various kinds, while many large bright-coloured fruits of 

 the tropics do not seem to be eaten at all. Many of these 

 are very round and smooth, and may get dispersed by 

 mere rolling down hill, as occurred with the mango in 

 Jamaica,^ or by being accidentally disturbed by the feet 

 of animals. It is to be observed, too, that the fruits of 

 trees are usually so abundant that, if eatable, there is no 

 danger of their not being eaten even if uncoloured, as in 

 the case of our acorns, beech-nuts, and chestnuts. An 

 immense number of the tropical fruits eaten by monkeys 

 and parrots are not coloured, and the half-developed seeds 

 are often alone eaten ; while in others, as the jack-fruit, 

 bread-fruit, and durian, the large seeds are as eatable as 

 the pulpy mass, and the edible nature of the fruit must be 

 injurious rather than otherwise as leading to the destruc- 

 tion of seeds. This need be no difficulty when we con- 

 sider that with forest trees, which live for several centuries, 

 there is only vacant space for young trees at long intervals, 

 and thus no rigid selection of seeds takes place tending to 

 secure them from being destroyed as food for animals. 



' See Sir Joseph Hooker's lecture at the Royal Institution on "The Dis- 

 tribution of the North Aiaerican Fljra." 



On account of the fondness of most birds and other 

 animals for the very same fruits which we like best, Mr. 

 Allen maintains the general community of taste in all 

 animals. I have, however, usually found monkeys eating 

 fruits which were very disagreeable to me, and the theory 

 is hardly consistent with the fact that many nauseous 

 fruits are bright-coloured. Thus the Citrullns colocynthus 

 of Palestine has a beautiful fruit of the size and colour of 

 an orange, but, according to Canon Tristram, " nauseous 

 beyond description to the taste," — while the Solatium 

 sanction, gQntraWy called the " Dead Sea apple," is almost 

 equally disagreeable, but is of a brilliant red colour. Now 

 if these fruits are eaten by any animals their taste must 

 be very different from ours, while if they are not, these 

 fruits have become strikingly attractive from other causes 

 than to induce animals to eat and disperse them. This 

 latter view is supported by another fruit, also found in 

 Palestine, the Calotropis procera, which is as large as an 

 apple and bright yellow, but is full of thin flat seeds winged 

 with exquisitely fine silky filaments. Here, then, the 

 seeds having special powers of dispersal by the wind do 

 not need the aid of animals, yet the fruit is most attrac- 

 tively coloured. This is one of the Apocynaceas, which 

 are usually poisonous, and I have observed brilliantly 

 coloured fruits of the same order in the tropics, but some 

 of these are known to be eatable. Taking into considera- 

 tion all the facts, it seems probable that attractive fruits 

 are more abundant among the smaller trees and shrubs 

 of temperate lands than in the forests of the tropics, and 

 that their colours are largely due to those adventitious 

 causes which our author has himself so well elucidated. 

 When their distribution has been aided by birds their 

 colours, their edibility, and the non-digestibility of their 

 seeds would all be increased by natural selection. The 

 dry fruits of herbaceous plants, in which the struggle for 

 existence is probably more severe, have no doubt often 

 been prevented from acquiring bright colours by natural 

 selection in order to protect their seeds, just as so many- 

 insects and birds have acquired brown or green protec- 

 tive tints. 



A curious point in relation to this question, and one 

 that has not been noticed by our author, is the very dif- 

 ferent characteristic colours of fruits and flowers. I have 

 tabulated the colours of these, under four heads, taken 

 from two books of manageable size — Hooker's " British 

 Flora" and Mongredien's ''Trees and Shrubs for English 

 Plantations." The colours of the two classes I find to 

 be as follows, dividing the purples between the red and 

 blue to the best of my judgment, and taking black among 

 fruits as corresponding to blue in flowers. 



Totals 



14 



68 



45 



Here we see that white and yellow which immensely pre- 

 ponderate in flowers are very scarce among fruits, among 

 which red and blue (or black) predominate, the two 

 colours which are far less common in flowers. We must 



