190 



Officers of Philadelphia Agricultural Society. Vol. XII. 



days — I write September 1st, — has unfortu- 

 nately verified — at least partly — the truth of 

 my anticipation. Previous to the heavy 

 rain wiiich fell throughout this district in 

 the thunder storm of the 16th of August, 

 I heard no complaint of disease; 1 had 

 not a vestige of it in my own garden, nor 

 could I hear of it in those of my neighbours, 

 with one exception, and that of a limited 

 character. Between the 16th and 20th of 

 August rumors of disease in this neighbour- 

 hood sprung up, and by the 30th it became 

 general. In some instances the loss is as 

 great as in 184.5. We thus find that in the 

 three years tiiis pestilence has destroyed our 

 potatoe crop, it has invariably exhibited itself 

 most severely and extensively between the 

 15th and 3lst of August. This fact allowed, 

 we make one step towards a rational descrip- 

 tion of the disease. Now, with regard to 

 its nature; it appears in different parts of 

 the plant at the same time, in the form of 

 small black patches, resulting from the death 

 of a portion of thp tissue of the plant. These 

 blotches in the leaves are generally dry, and 

 crumble beneath the touch, and in some in- 

 stances are covered with a parasitical fun- 

 gus, the Botrytis lufestans. No person, I 

 think, who has had the slightest experience, 

 will fall into the great error of attributing 

 the accession of the blotches to the injury 

 caused to the leaf by an apliis, or any other 

 insect. The two phenomena are widely 

 different. The aphis causes the leaves 

 which it infests to curl and form hollows, in 

 which it generally is found to congregate in 

 large numbers long before the vitality of the 

 leaf is affected. This is not the case with 

 the potatoe disease. I have looked carefully 

 through my rows without finding an aphis 

 of any description; but there is no mistaking 

 the dark, isolated, gangrenous-looking spots, 

 which are appearing on the leaves, along 

 the stems, and among the tubers. IIow is 

 this? 1 take up a root, and find five tubers 

 perfectly sound and one diseased. I look at 

 once at the stem and leaves, and find patches 

 of the well known disease isolated, perfectly 

 distinct from each other. Now I know of 

 no law in vegetable physiology which en 

 ables an insect to cause phenomena like 

 these. The notion is too absurd ; it will not 

 bear a moment's examination. In one of my 

 deductions last year, I suggested the soi" 

 might have a greater or less influence in 

 effecting a change in the vital process; but 

 I find tiiat the gardens on our rail-road, 

 some of which are many feet below the 

 usual surface, are all infected. One attri 

 bute of the soil I feel quite convinced has 

 considerable influence over this disease, viz: 

 its moisture. I have planted some potatoes 



in a line, part of which are among goose- 

 berry bushes and very damp; the other por- 

 tion is very dry. In the former the potatoes 

 are nearly all diseased, in the latter they 

 are nearly all sound. With regard, then, to 

 the nature of this disease, I think we may 

 fairly define it "gangrene of the plant, oc- 

 curring in the first instance in isolated 

 patches, either in the leaves and stem alone, 

 or simultaneously in the tuber, which if left 

 alone will ultimately destroy the plant and 

 tubers entirely." Nearly 200 years ago, 

 Sydenham described a species of cholera 

 affecting the human subject in August. Pop- 

 ular error has generally attributed this dis- 

 eaf^e to the plum season ; but this is a great 

 mistake. The disease described by Syden- 

 ham may have been studied by many ob- 

 servers in 1847, without a variation in the 

 symptoms. It occurs in those M'ho do not 

 eat plums, and the disease caused by plums 

 is not that described by Sydenham. It is, 

 in fact, one of those periodic phenomena of 

 which we know little more than its appear- 

 ance and disappearance at certain seasons of 

 the year, and which we judge by analogical 

 reasoning is caused by some or other of those 

 little understood, or rather little studied, laws 

 which belong to the science of meteorology. 

 That the potatoe disease belongs to the same 

 class of diseases must, I think, be perfectly 

 clear. It has all the characters, all the va- 

 riations, and all the obscurity of a periodical 

 epidemic. We may describe it as "Morbus 

 niger — a gangrene of the tissues of the po- 

 tatoe plant occurring epidemically in Au- 

 gust; the diseased parts generally covered 

 with a fungus, which appears subsequent to 

 the disease. More extensive in cold and 

 damp situations." More than this, so far as 

 regards the etiology of the disease, I do not 

 think we shall ever know. — Gardener^s 

 Chronicle. 



Officers of Philadelphia Agricultural 

 Society. 



At the annual meeting of the Philadel- 

 phia Society for promoting Agriculture, held 

 on the 5th inst., the following named gentle- 

 men were elected to serve as officers for the 

 ensuing year. 



President — A. S. Roberts. 



Vice Presidents — Dr. A. L. Elwyn and 

 Robert T. Potts. 



Rec. Secretary — Aaron Clement. 



Assistaitt Rcc. Secretary — P. R. Freas. 



Corresponding Secretary — Owen Jones. 



Treasurer — George Blight. 



Ctiralors — David Landreth and S. S. 

 Richie. 



Librarian — Aaron Clement. 



riiiladelphia, Jan. 6lh, 1848. 



