Vll 



PAPERS. 



Mr. Bastow then read a paper on the Peronospora infestans, or 

 potato disease, in which he pointed out the life history of this de 

 structive fungus. Having alluded to Messrs. Cooke, Berkeley, De Bary, 

 and more especially to Mr. W. G. Smith as having worked most 

 assiduously on this subject. He stated that when the potato plant is 

 attacked by the fungus the leaves assume a pale tint, become spotted, 

 and are covered with white mealy patches on the under surfaces. 

 The plant quickly withers, and the spores formed within it spread de- 

 struction over the whole field. Examined by the microscope the white 

 patches present a beautiful appearance, something like a miniature 

 crystal forest, with each branch bearing fruit. When the fruit 

 cases open, zoospores are scattered right and left, these have the 

 power of movion, and working their way into the fluids of the plant, 

 their cilia drop off, and the zoospore, (to all appearances a minute 

 member of the animal kingdom) at once begins to throw out mycelium 

 threads and fertile stems, once more bearing fruit. They propagate 

 also by resting spores, these resting spores being oginia that have 

 been fertilised by having almost wholly absorbed antheridia. Slides, 

 containing specimens of the potato plant infested with this fungus, 

 Were shown under the microscope with an eighth of an inch objective. 

 The fertile stems had all the appearance of small hyaline trees, the 

 branches being simple or with short branchlets. The zoospores could 

 be made out as they rested in their fruit cases. De Bary states that 

 19,G20 of these zoospores are contained in one square line, so that there 

 need be no surprise that acres of potatoes are destroyed in so short a 

 space as 43 hours. 



Mr. Shoobridqe said he never knew, in his experience, of that 

 disease in Tasmania. 



Mr. Johnston" asked if this disease had appeared to any extent in 

 Tasmania. 



Mr. Shoobridge said it had not appeared in his district, and he had 

 Hot heard of it having broken out in the colony. 



The Chairman : I don't think it is known in this colony. 



Mr. Stephens : It is to be hoped that it never will be. 



Mr. Shoobridcje : It is similar to the Irish blight. 



Mr. Bastow : Yes. 



Mr. S1100P.RIDGE said that the only disease he knew in Tasmania- 

 affected the tubers only. 



Mr. Stephens said there was a disease among the potatoes in the 

 colony which required investigation, because its history and origin was 

 not very well known. 



Mr. Johnston suggested that Mr. Bastow be asked to examine some 

 °f these diseased potatoes, and bring a paper before the society on the 

 subject. 



■Mr. Stephens said that a peculiar characteristic of this disease was 

 that it was always accompanied by a peculiar change in the weather, 

 weakening the plant and rendering it more susceptible. He was in Eng- 

 land all through the potato blight, and he found that the only soil where 

 potatoes would gro iv free of disease was a sandy ground. The only 

 place which he knew where the potato blight did not extend was on 

 a cultivated beach at Morecambe Bay, which was little more than 

 sand, but, of course, was strongly impregnated with salt. He hoped, 

 however, that they would not get the disease in Tasmania. 



Mr. Johnston said that in the north highlands of Scotland many large 

 tracts of land which had at some recent period been covered by the 

 sea were planted with potatoes. The potatoes grew better on a 

 shingly beach than anywhere else, and those grown inland were found 

 to be more affected with disease. 



