The Besting Sjpores of the Potato Fungus. By W. G. Smith. 127 
other times the oogonium shows a distinct differentiation in its 
contents, and matures from one to three resting spores, which to 
me shows an approach to the condition of the vesicle which usually 
gives birth to the zoospores. — See also the ' Gardeners' Chronicle,' 
July 17 and 24, from which the above Plates have been taken. 
Since the above observations were printed, the following facts 
have been observed by me, and recorded in the 'Gardeners' 
Chronicle' for July 31. 
1. Some plants sent to the Koyal Horticultural Society by Mr. 
Dean on July 21 were covered with the Peronospora far beyond 
anything I had ever seen before. The haulm, the leaves (on both 
sides alike), and the berries, were covered. Some of these plants, 
after being placed on a garden bed, and covered with leaves (to 
keep them moist), were the next day one white mass with the 
Peronospora. 
2. The Potato fungus (as commonly seen) bears a far larger 
number of simple-spores than inflated vesicles containing the 
zoospores or swarm-spores, but in Mr. Dean's plants the fungus 
produced zoospores almost exclusively, and in the greatest abun- 
dance. As the zoospore is a higher development of the plant than 
the simple-spore, this latter observation points to the unusually 
robust health of the fungus this season. 
3. On suspending the infected leaves over a glass of water for 
from twelve to seventy-two hours, the swarm-spores fell in abun- 
dance (either free or in the vesicle) on to the water, and there 
germinated. No single drop of the water could be taken up for 
examination without meeting with the germinating spores, the 
threads radiating over the water in every direction, evidently in 
quite a congenial element. It brought the following fact to light, 
which is of importance — some of the vesicles which usually dis- 
charge the zoospores discharged instead a thick mass of mycelium ; 
and this cord, when it had proceeded a considerable distance over 
the water, there had its contents differentiated in a necklace-like 
manner, and gave birth to the zoospores far removed from the 
original vesicles. The same .thread also produced two true oogonia 
on the water. 
4. At the meeting of the Scientifi:c Committee of the Koyal 
Horticultural Society, held on July 21, Mr. Kenny showed a 
species of Saprolegnia which, he said, might be mistaken for Pero- 
nospora. But if reference is made to my original paper it will be 
seen from the first that I have perceived the intimate connection 
between the new condition of the Potato fungus and the Sapro- 
legnieae. On my side I have the high authority of Thuret and 
Berkeley for similar alternation in the diseases of silkworms, flies, 
&c. I am quite prepared, therefore, to consider Mr. Kenny's plant. 
