The Potato Fungus, By WortMngton G. Smith. 133 
Peronospora springs direct, and (when artificially grown) almost 
invariably in a- terminal manner. The conidia are not mature in 
any of the specimens here figured ; doubtless this is because all the 
plants are more or less abnormal from being grown artificially, but 
still the threads are characteristic of Peronospora infestans, and no 
known fungus but the one which causes the Potato disease has 
vesicular swellings such as are shown at P. 
Mr. Chas. B. Plowright (surgeon, of King's Lynn, a gentle- 
man who has long studied fungi) has patiently examined some of 
the living material with which I have been working this spring 
and early summer, and he writes me on May 19 to say : "I find 
plenty of branching, nodose conidiophores, especially amongst the 
drier portions of the substance sent. I also see living conidia. I 
have seen many conidiophores with convoluted bases, but in the 
vast majority of cases long ere the conidia come the oospore is 
gone ; I see the granular protoplasm distinctly ascending the base 
of the conidiophore." As regards the first coil of mycelium, Mr. 
Plowright writes : " I distinctly saw this curved in two oospores, 
and I believe the mycelium comes out with a curl." The same 
gentleman, under date May 19, writes : " I saw a great many 
conidiophores both with conidia in situ and not ; most conidia had 
fallen off" ; latterly I saw plenty of convoluted bases." The 
evidence of identity appears complete, and many of the figures 
here published, and others not published, have been confirmed by 
Messrs. Vize and Plowright. 
At Q, Plate CLIV., may be seen Peronospora mycelium with a 
young plant (Q^) growing from amongst the starch of the Potato 
tuber, the dark background showing the cell-wall corroded by the 
fungus, and at E a similar fragment of mycelium upon the cuticle 
of a Potato leaf ; it is very common to see one cell of the cuticle 
thus discoloured by the corrosive mycelium, the corrosion of the 
cell being caused by the mycelium passing over and upon it. 
Both threads here shown come direct from last year's resting 
spores. At S is engraved a branch of the Potato fungus, showing 
the numerous partitions with which the threads are at times fur- 
nished, and at T is a typical well-grown branch of the fungus, with 
a full'grown conidium at the apex ; this conidium may either dis- 
charge zoospores, as at U, or an irregular mass of protoplasm, as at 
Y, from either of which a new plant may spring, and in this habit 
the conidium agrees well with the resting spore ; the branch in this 
figure is shown as continuous, and though furnished with the vesi- 
cular swellings no partitions are present, the branches are frequently 
so seen. At W is illustrated a small weak plant, giving rise to a 
branch, which branch is developing into a large and strong plant ; 
such a phenomenon is by no means uncommon, and shows how the 
fungus may at times be proliferous and how it increases itself in 
