Rain-tree.—

At the close of 1877 a paragraph went the round of the papers describing, on the authority of the United States Consul at Loreto, a tree existing in the forests near Moyobamba in Northern Peru.—"The tree is stated to absorb and condense [the humidity of the atmosphere with astonishing 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."

This singular story led to many applications to Kew, amongst others, from the India Office on behalf of the Agri-Horticultural Society of Madras and from the Société Economico-agraria of Malta.

Professor Ernst, of the University of Caracas, had already published a very similar account in the "Botanische Zeitung "(1876, pp. 35, 36). The tree observed was Pithecolobium Saman. Professor Ernst states:—"In the month of April the young leaves are still delicate and trans parent. 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." Professor Ernst attributes the "rain" to secretion from glands on the foot-stalk of the leaf on which drops of liquid are found, which are rapidly renewed on being removed with blotting paper.

Mr. Spruce, the well-known South American traveller, has, however, obligingly supplied us with an explanation which appears quite complete page 47 as far as the original Moyobamba rain-tree is concerned. He writes:—

"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 first witnessed the phenomenon in September 1855 when residing at Tarapoto (lat. 6½° S., long. 76° 20′ W.), a town or large village a few days eastward of Moyobamba. . . . A little after 7 o'clock we came under a lowish spreading tree, from which, with a perfectly clear sky overhead, 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. . . . 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 omnivorous cicada, might become (pro tem.) a Tamia-caspi or rain-tree. This particular tree was evidently, from its foliage, an Acacia. Among the trees on which I have seen cicadas feed is one closely allied to the Acacias, the beautiful Pithecolobium Soman . . . . Another leguminous tree visited by cicadas is Andira inermis, and there are "many more of the same and other families which I cannot specify. . . . .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 21 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."

This and other information was communicated to "Nature" by the Assistant Director (28th February 1878, pp. 349, 350). So much is reproduced here for the information of correspondents of Kew, many of whom continue to make inquiries upon the subject.

Professor Ernst is still of opinion that in Venezuela the Pithecolobium Saman produces a rainy mist without the intervention of insects. In Jamaica and India the occurrence has not, however, been observed.

In the early part of the last century a similar story was placed on record, and is to be found in "A "Journey Overland from the Gulf "of Honduras" by John Cockburn (London, 1735, pp. 40-42).

"Near the mountains of Vera Paz (Guatemala) we came out on a large plain where were numbers of fine deer, and in the middle stood a tree of unusual size spreading its branches over a vast compass of ground. We had perceived at some distance off the ground about it to be wet, at which we began to be somewhat surprised, as well knowing there had no rain fallen for near six months past. At last, to our great amazement, we saw water dropping, or, as it were, distilling fast from the end of every leaf."