HARDWICKE'S SCIENCE-GOSSIP. 



223 



in that year, and published in Saunders's Xetcs 

 Letter, gives a graphic account of its ravages. The 

 letter says :—" During the months of July and 

 August we had repeated and heavy showers, with 

 oppressive heat, and an atmosphere strongly charged 

 with electricity. Towards the close of the month 

 of August I observed the leaves to be marked with 

 black spots, as if ink had been sprinkled over them. 

 They began to wither, emitting a peculiar offensive 

 odour ; and before a fortnight, the field, which had 

 been singularly luxuriant, and almost rank, became 

 arid and dried up, as if by a severe frost. I had the 

 potatoes dug out during the mouth of September, 

 when about two-thirds were either positively rotten, 

 partially decayed, and swarming with worms, or 

 spotted with brownish-coloured patches, resembling 

 flesh that had been frost-bitten. These parts were 

 soft to the touch, aud upon the decayed potatoes I 

 observed a whitish substance like mould." From 

 careful consideration of the earliest recorded cases 

 of this disease, there can be little doubt of its 

 American origin, or indeed from its dating back 

 from a very early period. A superficial thinker 

 might be inclined to fall back upon the theory of 

 " spontaneous generation," and so account for the 

 origin] of the potato fungus, about ISiO; but 

 although Feronospora infestaiis belongs to a genus 

 numbering some forty species, all more or less 

 alike, and all parasitic upon living plants, yet 

 the specific characters of P. infestans appear so 

 distinct (such as in the peculiar swellings on the 

 thread-like stems, &c.), that no observer of natural 

 objects accustomed to distinguish one thing from 

 another, could for a moment think of considering 

 P. infestans as a mere form of some immediate ally. 

 Its real origin, like the origin of all plants, animals, 

 diseases, &c., probably dates into the far past, and 

 is likely to be ever involved in obscurity. Nothing 

 is so difficult (or even impossible) as to trace things 

 to a beginning : this has often been attempted in 

 regard to the diseases with which man is aifected, 

 but with little success ; no one can tell how or from 

 whence scarlet and typhus fever and other ailments 

 really originated. Epidemic cholera is said to have 

 originated in the delta of the Ganges in 1S17 ; but 

 it seems highly probable (if this or anything else 

 ever had a beginning), that if a searching investiga- 

 tion were made, its real origin would date from 

 remote antiquity. It is not generally known that 

 the fungus which produces the potato disease is by 

 no means confined to potatoes, but attacks other 

 members of the family to which the potato belongs ; 

 for instance, it is very common on the fruit of the 

 tomato, and has been detected on the common 

 woody-nightshade, or bitter-sweet of our hedges 

 {Solanum Dulcamara); it even does not confine itself 

 to the family to which the potato belongs {Solana- 

 ceee), but has been found upon Anthoceris viscosa, 

 a member of the Scrophulariacea; ; therefore, in 



searching into the " origin" oi Feronospora infestans, 

 we not only have to look to the beginning of the 

 potato disease itself, but to the diseases of such 

 plants as the woody-nightshade and tomato. Little 

 was kmion of the disease as affecting potatoes in 

 this country till July, ISiS, when it ravaged the 

 south of England, the first printed record of its 

 alarming advent appearing in a letter from Dr. 

 Salter, in the Gardener's Chronicle for Aug. IG. So 

 rapid and devastating now was its progress in this 

 country, that Mr. Berkeley states few sound pota- 

 toes were to be found in Covent Garden market a 

 fortnight after its first recorded appearance, and 

 though at this time it had not reached the Midland 

 Counties, yet in a few days it was general. At 

 the beginning of September it was recoi'ded from 

 Ireland, and a few days afterwards from Scotland, 

 at which time the full power of the potato murrain 

 was expending itself upon the British isles. About 

 this period (as now) the leading newspapers teemed 

 with balderdash and the most alarming, absurd, and 

 contradictory accounts, some writers attributing 

 the disease to an epidemic resembling cholera; 

 others to animal manure used in cultivation, to 

 microscopic insects, railways, or electric influences ; 

 whilst some persons asserted it was a sign of the 

 break-down of the potato-plant from over-cultiva- 

 tion ; or that it was caused by the tubers being cut 

 in pieces before planting. All the papers, grave or 

 gay, had something to say about it, and the potato 

 disease was even one of the stock subjects reserved 

 to joke about in the Christmas pantomimes. On 

 one stage a gigantic tuber was brought on sur- 

 mounted by an equally gigantic aphis, a joking 

 allusion being at the same time made to the Aphis 

 vasi-tater. So serious, indeed, was the state of 

 things at this period, that three of the Governments 

 of Europe issued commissions to examine into the 

 cause of the murrain, and discover, if possible, the 

 remedy. It has frequently been remarked, that 

 just before a bad attack of the disease the leaves 

 and stems of the potato become a darker green and 

 appear more than usually luxuriant, as stated in the 

 letter addressed to Dr. Bellinghara above quoted. 

 This has been accounted for from the fact that the 

 mycelium of fungi is a great incentive to the pro- 

 duction of the green colouring matter of leaves ; we 

 may, therefore, safely assume that this appearance 

 is put on immediately after the germination of the 

 spores upon the foliage and stems. So rapid is the 

 growth of this parasite, that in four or five days 

 after this germination the tissues of the leaves 

 become traversed in every direction by the 

 mycelial threads, and the fruit-bearing branches 

 are protruded through the breathing-pores on the 

 under side of the leaves, as shown in fig. 153. The 

 parasite never appears on the upper surface, which 

 is impervious to its attacks ; but in perfecting 

 itself, and producing its abundant fruit, it totally 



