October 17, 1S72. ] 



JOUBNAL OF HOETICULTUBE AND COTTAGE GABDENEB. 



307 



possible), as to trace things to a beginning : this has often 

 been attempted in regard to the diseases with which man is 

 affected, 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 1817 ; but it seems highly probable (if 

 this or anything else ever had a beginning), that, if a searching 

 investigation 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 be- 

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

 Tomato, and has been .detected on the common Woody Night- 

 shade, or Bitter-sweet of our hedges (Solanum Dulcamara) ; it 

 even does not confine itself to the family to which the Potato 

 belongs (Solanaeea?), but has been found upon Anthoceris 

 viscosa, a member of the Scrophulariacea; ; therefore, in search- 

 ing into the " origin" of Peronospora 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 known of the disease as affecting 

 Potatoes in this country till July, 1815, when it ravaged the 

 south of England, the first printed record of its alarming 

 advent appearing in a letter from Dr. Salter, in the Gardeners' 

 Chronicle for August 16. So rapid and devastating now was 

 its progress in this country, that Mr. Berkeley states few sound 

 Potatoes were to be found in Covent Garden Market a fort- 

 night 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 

 recorded from Ireland, and a few days afterwards from Scot- 

 land, at which time the full power of the Potato murrain was 

 expending itself upon the British isles. About this period (as 

 bow) 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 person 

 asserted it was a sign of the break-down of the Potato plant 

 from over-cultivation ; 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 surmounted by an equally gigantic aphis, a joking 

 allusion being at the same time made to the Aphis vast-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. Bellingham above 

 quoted. This has been accounted for from the fact that the 

 mycelium of fungi is a great incentive to the production 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. 1. The 

 parasite never appears on the upper surface, which is im- 

 pervious to its attacks ; but in perfecting itself, and producing 

 its abundant fruit, it totally destroys the matrix on which it 

 grows, and causes the leaves to putrefy and dry up. Perfect 

 specimens are seldom met with on Potato stems ; but the de- 

 structive mycelial threads descend them, and so reach the tuber. 

 The stem now, like the leaves, rapidly rots, and falls upon the 

 earth an offensive mass. So rapid and fatal is the growth of 

 this fungus, that in a few days it will spread from plant to 

 riant over a large tract, and in less than a week turn every 

 stem and leaf in the field to one rotten mass. Within these 

 diseased stems are often found black masses of hardened 

 threads, which are believed to be the mycelial filaments, in a 

 resting and highly condensed, but still living state : these black 

 threads have been described under the name of Sclerotium 

 varium. Another form of this substance, very common just 

 under the bark of old trees, has been described under the 

 name of Bhizomorpha ; this is probably the mycelium, of some 



Polyporus in a high state of condensation : similar threads 

 have also been found on the woodwork of old coffins. Beturn- 

 ing to the young condition of the Potato fungus, we see it five 

 days old in fig. 1, where the distance from a to b shows the 

 thickness of the Potato leaf itself, magnified four hundred 

 diameters : a is the upper surface of the leaf, and b the lower. 

 The mycelial threads or spawn, c, may be seen ramifying 

 amongst the cellular tissue of the leaf, whilst the fertile thread 

 is shown emerging through a breathing-pore, or stomate, d, 

 and branching and bearing (at present) immature spores at E. 



Fig. 2.— Peronospora infestans, enlarged 150 diameters. 



It is almost impossible to conceive of anything which eould 

 have a more damaging effect upon a plant than such a growth 

 as this ; for, leaving out the destructive nature of the mycelium 

 within the leaf, the whole of the leaves' mouths, or breathing- 

 pores, soon become completely choked-up. It is somewhat 

 analogous with a bad attack of croup in the human subject, 

 with the addition of an external growth. Fig. 2 represents 

 the mature condition of the fungus enlarged to 150 diameters 

 only : here the characteristic swellings on the branched threads 

 are shown, the stems bearing an abundance of spores (which 

 are analogous with seeds, and reproduce the parent), on their 

 apices ; the threads, as in the last figure, are seen emerging 

 through a breathing-pore on the lower surface (here inverted, 

 better to display the character of the fungus). — Woethington 

 G. Smith, F.L.S. (in Hardwicke's Science-Gossip.) 

 (To be continued. ) 



Potatoes eeoh the Continent. — During the past week there 

 have been very large importations of Potatoes from France, 

 Belgium, and Holland at Great Grimsby. The Potatoes are 

 packed in bags, weighing eight stones, and meet with a ready 

 sale at 7s. Gd., a-bag from local dealers. There are no symptoms 

 of disease among them, and the importation has been not less 

 than 200,000 pecks during the past week. Preference was given 

 to the Potatoes brought by the City of Ghent from Ghent, 



