INDUSTRIAL PROGRESS DURING THE YEAR 1875. ccxi 



upper surface of the leaf which secrete au acid juice by which 

 the captured insects are digested. In Drosera, when any- 

 body has been caught by the sticky fluid at the end of a hair, 

 an impulse is conveyed through the hair to those on other 

 parts of the leaf, which causes them to bend over until they 

 touch the object caught. They then secrete an acid juice by 

 which it is digested. In Utricularia, the insects caught in 

 the leaf-bladders slowly decompose. Darwin has made very 

 careful investigations on the process of digestion in Drosera 

 and Dionasa, and comes to the conclusion that the secreted 

 fluid in both cases is closely allied to, if not identical with, 

 the gastric juice. Although contact of almost any foreign 

 body will cause, in one case, the hairs to bend over toward 

 it, in the other the leaf itself to close suddenly, the digestive 

 power of the secreted fluids in both cases is only capable of 

 digesting nitrogenous substances. Salts of ammonia seem to 

 have the greatest effect on the hairs of Drosera, and espe- 

 cially phosphate of ammonia, extremely minute quantities of 

 which have a powerful effect. The leaves of both Drosera 

 and Dionoea seem to be insensible to falling drops of rain and 

 currents of air. 



Distribution of Seeds. At the request of M.Alphonse de 

 Candolle, a number of experiments were made by M. G. Thu- 

 ret, of Antibes, France, to ascertain how long different seeds 

 and fruits would float on salt water. He concludes, contrary 

 to the opinion of Martins, that distribution of plants by 

 means of ocean currents can take place only to a very lim- 

 ited extent, as in by far the greater number of his experi- 

 ments seeds and fruits sank either at once or in a few days. 

 M. Thuret also experimented on the power of germination of 

 seeds after continued immersion in salt water. Out of the 

 seeds of thirty-three species, which w T ere immersed for thir- 

 teen months, twenty-four were in good condition and w T ere 

 sown in pots. Of these twenty-four, ten grew. 



Disease of Orange -trees. The orange-trees of California 

 have lately been attacked by the fungus Capnodium Citri, 

 Berk, and Desm. The disease is recognized by the leaves 

 being covered w T ith a blackish powdery substance, which 

 can without difficulty be wiped oft*. At the same time a 

 disease attacked the olive-trees. The name given to the 

 fungus in the latter case is Antennaria daiophila* This is 



