Feb. 28, 1878] 



NATURE 



349 



offices, as all messages of the most private nature can be 

 sent without publicity, an advantage possessed by no 

 other system. 



It is unnecessary to point out any other of the many 

 practical applications to which this auto-kinetic system 

 may be applied. It is a system that must shortly extend 

 its social metallic nerves to all the large centres of com- 

 merce and manufacture in this kingdom, and its various 

 applications will then become more fully developed and 

 known. 



THE RAIN-TREE OF MOYOBAMBA 



SOME little while since a paragraph went the round of 

 the papers, describing, on the authority of the United 

 States Consul in the province of Loreto, a tree existing 

 in the forests near Moyobamba, in Northern Peru. 



According to the Madras Times and Overland Mail of 

 December 15, 1877, "The tree is stated to absorb and 

 condense the humidity of the atmosphere with astonish- 

 ing energy, and it is said that the water may frequently 

 be seen to ooze from the trunk, and fall in rain from its 

 branches in such quantity that the ground beneath is 

 converted into a perfect swamp. The tree is said to 

 possess this property in the highest degree during the 

 summer season principally, when the rivers are low and 

 water is scarce, and the Consul therefore suggests that 

 the tree should be planted in the arid regions of Peru, for 

 the benefit of the farmers there." 



As always happens in cases of this kind, there have not 

 been wanting those who have taken this singular story quite 

 seriously, and the India Office has applied to the Royal 

 Gardens, Kew, on behalf of the Agri-Horticultural Society 

 of Madras for information about the tree. It may be 

 interesting to some of the readers of Nature, and it will 

 certainly save future correspondence, if I explain once 

 for all what I have been able to ascertain as to the origin 

 of the fable and the amount of truth which it contains. 



Poeppig's " Reise in Chile und Peru" (2 vols., 1835), 

 which contains much useful botanical information, appa- 

 rently makes no reference to the subject. 



I am indebted to Dr. Francis Darwin for pointing out to 

 me a very similar account which appears in the Botanische 

 Zeitung, January 21, 1876, pp. 35, 36, in which Prof. Ernst, 

 of the University of Caracas, records his observations 

 upon a tree oi Piihecolobitun {Calliandrd) Santa?!,, Benth. 



" In the month of April the young leaves are still 

 delicate and transparent. During the whole day a fine 

 spray of rain is to be noticed under the tree, even in the 

 driest air, so that the strongly-tinted iron-clay soil is 

 distinctly moist. The phenomenon diminishes with the 

 development of the leaves, and ceases when they are fully 

 grown." 



I found that the specimens of this tree in the Kew 

 Herbarium brought its range close to Moyobamba, as 

 they included some gathered by the traveller Spruce, 

 near the neighbouring town of Tarapoto. It appeared 

 probable, therefore, that the Tamia-caspi — the name given 

 in one variant of the story — was Pithecolobinm Saman, 

 though the cause of the rain was more mysterious than 

 ever. Being vouched for by so competent an observer as 

 Prof. Ernst, its occurrence could not well be denied, 

 while on the other hand, the Pithecolobinm being a well- 

 known cultivated tree in the West Indian Islands, it was 

 quite clear that if the " raining " from its foliage were a 

 normal occurrence, it would long ago have been put on 

 record. 



Mr. Spruce has, however, obligingly supplied me from 

 the astonishing stores of information which he possesses 

 with the true history of the whole matter, and he has also 

 been so good as to allow me to communicate to the 

 readers of Nature the substance of what he has told me. 



" The Tamia-caspi, or rain tree of the Eastern Peruvian 

 Andes, is not a myth, but a fact, although not exactly in 



the way popular rumour has lately presented it. I did 

 not know there was any doubt as to the true origin of the 

 ' rain.' I first witnessed the phenomenon in September, 

 1855, when residing at Tarapoto (lat. 6^° S., long. 76° 20', 

 W.), a town or large village a few days eastward of 

 Moyobamba, and little more than 1,000 feet above the sea- 

 level. I had gone one morning at daybreak, with two 

 assistants, into the adjacent wooded hills to botanise. 

 .... A little after seven o'clock, we came under a lowish 

 spreading tree, from which with a perfectly clear sky over- 

 head a smart rain was falling. A glance upwards showed 

 a multitude of cicadas sucking the juices of the tender 

 young branches and leaves, and squirting forth slender 

 streams of limpid fluid. We had barely time to note this 

 when we were assailed by swarms of large black ants, 

 which bit and stung fiercely, and obliged us to beat a 

 retreat, my companions calling out as they ran ' Tamia- 

 Caspi ! Tamia-Caspi ! ' When we had shaken off our 

 assailants, I ventured to approach the spot so near as to 

 make out that the ants were greedily licking up the fluid 

 as it fell. . . . 



" My two Peruvians were already familiar with the 

 phenomenon, and they knew very well that almost any 

 tree, when in a state to afford food to the nearly omnivo- 

 rous cicada, might become {pro tern) a Tamia-caspi, or 

 rain-tree. This particular tree was evidently, from its 

 foliage, an Acacia, but as I never saw it in flower or fruit, 

 I cannot say of what species. I came on cicadas, simi- 

 larly occupied, a few times afterwards, and on tre6s of 

 very different kinds, but never without the pugnacious 

 ants on the ground beneath. Among the trees on which 

 I have seen cicadas feed, is one closely allied to the 

 acacias, the beautiful Pithecolobijnn Saman. The young 

 branches are very succulent, and they bear elegant bipin- 

 nate leaves. . . . The pods are greedily eaten by deer 

 and cattle. Another leguminous tree visited by cicadas 

 is Andira inermis, and there are many more of the same 

 and other families which I cannot specify. Perhaps they 

 avoid only such as have poisonous or strongly resinous 

 juices ; and those which are permanently tenanted by 

 ferocious ants such as all Polygoneoe, the leguminous 

 Platymisciutn, and a few others. . . . These ants rarely 

 leave the tree which affords them food and shelter, and 

 they jealously repel all intruders, the slightest scratch on 

 the smooth bark sufficing to call their sentinels to the 

 spot. They are quite distinct from the robust marauding 

 ants that drink the cicadas' ejectamenta. 



" I have no doubt you have above the true explanation 

 of the Tamia-caspi, or rain-tree. As to the drip from a 

 tree causing a little bog to form underneath and around 

 it, that is a very common circumstance in various parts of 

 the Amazon Valley, in flats and hollows, wherever there 

 is a thin covering of humus, or a non-absorbent sub-soil, 

 and the crown of foliage is so dense as to greatly impede 

 evaporation beneath it. On such sites the Achudl palm 

 {Mauritiajlexuosa) common enough between Moyobamba 

 and Tarapoto, as well as on the savannahs of the Orinoco, 

 and in subriparial forests of the Amazons — affords a 

 striking example of this property, as has already been 

 remarked by Gumilla, Velasco, Humboldt, and others. 

 Finally, although I never heard the name Tamia-Caspi 

 applied to any particular kind of tree, during a residence 

 of two years in the region where it is now said to be a 

 speciality, it is quite possible that in the space of twenty- 

 one years that have elapsed since I left Eastern Peru, that 

 name may have been given to some tree with a greater 

 drip than ordinary ; but I expect the cicada will still be 

 found responsible for ' the moisture pouring from the 

 leaves and branches in an abundant shower' — the same 

 as it was in my time." 



Mr. Spruce's notes are so precise and careful that there 

 is little difficulty in accepting his explanation of the rain- 

 tree. It is, however, hard to understand the omission of 

 all insect agency in the equally careful account given by 



