31 



disease, as the air penetrates more freely into the earth, and 

 the moisture passes off more freely. No one seems to know 

 exactly where the disease came from when it so suddenly 

 appeared in the Isle of Wight in 1844, all we know is that it 

 there appeared and that it spread very rapidly. 



It may be that the P. infestans is a descendant of a fossil 

 species Peronosporites anliquarius found amongst the vascular 

 bundles of a Lepidodendron from the coal measures, figured 

 and described in Science Gossip, Vol. XIII., p. 270. It 

 appears that the ovarian sacs visible in that fossil plant 

 contain zoospores as well defined as any to be obtained on 

 living plants, the septate mycelium being equally distinct. 

 The only difference appears to be that the host was not a 

 potato plant ; the genus Peronospora is not however confined 

 to solanacious plants. The eighteen at present known species 

 •of Peronospora attack parsnips, peas, onions, spinach, lettuce, 

 clover, nettles, anemones, poppies, roses, docks, etc., but 

 apparently not in such a destructive manner as P. infestans 

 does with potatoes. 



THE OCCULTATION OF JUPITER. 



By A. B. Bracts. 



Bead IQth April, 1886. 



As the visibility of an occultation, like that of a solar eclipse, 

 depends upon the position of the observer, the chance of such 

 an event being visible in any particular locality is rather 

 scanty. On looking down the list of southern occultations of 

 Jupiter for the current year, I saw there were three that came 

 temptingly near us. On working these out, I found that one, 

 that of 16th of April, was in a most favourable position for 

 observation, being near the meridian ; but, to my disappoint- 

 ment, that those for March 20th, and May 13th, would be just 

 missed by us ; the former being over just before the moon 

 would rise, and the latter commencing just after setting. On 

 20th March, I had both bodies in the same field of the 

 telescope at rising, the moon having passed the planet. 



With regard to the occultation of 16th April, I regret much 

 that, through my not having taken the precaution of obtaining 

 assistance to record notes, and being flurried by the clatter 

 caused by a boisterous wind upon my iron roof, I was not able 



