364 ANNUAL EECOKD OF SCIENCE AND INDUSTRY. 



ing from almost smooth and transparent bladders, to brown, 

 somewhat rough, and warted or echinulate spheres. Similar 

 ones had been previously observed in the natural growth 

 the previous summer, though no one then could account for 

 their origin. At the end of nine months germination began, 

 the resting spores became dense and dark, the oospore occu- 

 pying the whole of the oogonium, instead of floating freely 

 inside as in the immature spore ; the contents of many of 

 them were broken up into zoospores with two tails, which 

 live in this form somewhere between twelve hours and a 

 week, when they come to a rest and the tails disappear. 

 Many of the zoospores perished, but others threw out threads 

 of mycelium, which were destined at length to bear the co- 

 nidiphores of the potato fungus. The oospores which did not 

 produce zoospores protruded a thick, jointed thread, agree- 

 ing exactly with average Peronospora infestaois threads. As 

 any method of destroying the resting spores of these pests 

 depends upon a knowledge of their life-history, this contri- 

 bution of Mr. Smith will be welcomed as a move in the right 

 direction. The paper itself, with four plates, was first pub- 

 lished in the Gardeiier'^ s Ghronicle^l^l Q,\>. 39-42, and since in 

 Grevillea and the Monthly Microscopical Journal^ Sept.^ 1876. 



DISEASES OF OLIYE AND ORANGE TREES. 



Professor W. G. Farlow, of Harvard, has recently been in- 

 vestigating the disease of olive and orange trees, caused by 

 fungous growths, and has arrived at the following results: 

 The disease first attracts the eye by the presence of a black 

 fungus, which however is not the cause of it, but rather the 

 attack of some insect, which itself deposits a gummy sub- 

 stance on the leaves and bark, or so wounds the tree as to 

 cause some sticky exudation, on which the fungus especially 

 thrives. In seeking a remedy, we are to look farther back 

 than the fungus itself to the insect or w^hatever it may be 

 which has made the luxurious growth of the fungus possible. 

 It is the same on both olives and oranges, and has been de- 

 scribed by Tulasne as Fimiago salicioia, found on willows, 

 oaks, birches, hawthorn, quince, and pear, the stylospore- 

 bearing portion being the Gapnodiiun citri of Berkeley and 

 Pesmazieres, and the pycnidal form the Aiitennaria elceophila 

 of Montagne. Professor Farlow suggests as a remedy alka- 

 line soaps, strong as the trees will bear. 



