POTATO 



700 



POTENTILLA 



rally, the crop of England late in the summer of 1845. 

 July and August were unusually wet and cold, and early 

 in August there were sharp morning frosts. Immediately 

 after, the stems began to decay ; but the weather con- 

 tinuing wet, instead of their decay being dry, and 

 attended with the usual phenomena of their reduction 

 to mere woody fibre, the putrefaction was moist, and the 

 srnell attendant upon it precisely that evolved during 

 the decay of dead potato haulm partly under water. 

 The stem decayed, whilst the fibres connecting the 

 tubers with them were fresh and juicy. 



The disease was first noticed between 1840 and 1842, 

 at Boston, U.S.A., and in Norway and Denmark. By 

 the time it created such alarm in the British Isles, it 

 had established itself all over Western Europe, causing 

 incalculable loss. Besides the Potato, it also attacks 

 the Tomato, the British wild Solanum Dulcamara (Bitter 

 Sweet), and several exotic species of Solanum in gardens. 

 The nature of the disease was investigated in 1875 and 

 1876 by Worthington G. Smith. It is sometimes named 

 Peronospora infestans, but it differs from a true Perono- 

 spora, by each branch of the fruiting stern ending in a 

 conidium, or egg-shaped spore case, which is pushed on 

 one side by the axis of the branch continuing to grow in a 

 straight line, and producing other conidia, which are 

 in turn pushed on one side. Being considered distinct 

 for this reason it is now named Phytophthora infestans. 



The disease usually breaks out some time in August, 

 and is most virulent in wet seasons, which favour the 

 germination of the spores upon the leaves, and their 

 rapid growth afterwards. The first signs of the presence 

 of the disease are small brownish patches on the leaves, 

 which rapidly increase in size and number till the whole 

 of the foliage becomes infested and turns black. The 

 disease has really been making progress, previously, 

 inside the leaf, till the fruiting branches emerge through 

 the stomata, after which the spores are wafted far and 

 wide by the wind. The fungus also travels down the 

 stem, but takes longer to effect its destruction. Spores 

 are also washed down through the soil, till they come in 

 contact with the tubers, in which the fungus continues 

 to grow even after they are lifted and stored. Indeed, 

 the fungus remains in the tubers, and may be planted 

 with them to continue the disease, if they are not observed 

 to be diseased and discarded at the time of planting. 



Various remedies have been proposed and acted upon, 

 with greater or less success, but Potatoes enjoy greatest 

 immunity, when the season is relatively dry from the 

 end of J uly to the middle or end of September. Diseased 

 stems and leaves should be burned, and diseased tubers 

 similarly destroyed as preventive means. Wet, heavy 

 soils and low-lying situations should be avoided, where 

 possible, when planting. Protective moulding has been 

 of some service in preventing the spores from getting 

 washed down to the tubers. About the time the disease 

 breaks out, the Potatoes should be earthed up on one 

 side only, pushing the stems on one side, so that they 

 will hang over the furrows instead of the ridges. About 

 4 inches of soil should be heaped over the top of the 

 tubers. The most successful remedy is to spray the 

 foliage with Bordeaux mixture on the first appearance 

 of the disease and again about fourteen days later, to 

 destroy the spores and prevent their germination on 

 healthy foliage. 



Fusarium Solani is considered by some authorities 

 (particularly the German botanists, Reinke and Berthold) 

 to be the cause of Dry Rot in Potatoes. The same 

 botanists regard Bacterium navicula and Baccillus amylo- 

 bacter to be the cause of Wet Rot in the tubers. 



POTATO, or UNDERGROUND ONION. (Allium Cepa 

 proliferum.) Produces a cluster of bulbs or offsets, in 

 number from two to twelve, and even more, uniformly 

 beneath the surface of the soil. From being first intro- 

 duced to public notice in Scotland by Captain Burns, of 

 Edinburgh, it is there also known as the Burn Onion. 



Varieties. There evidently appear to be two varieties 

 of this vegetable, one of which bears bulbs on the summit 

 of its stems, like the Tree Onion, and the other never 

 throwing up flower-stems at all. One variety is much 

 larger than the other, and this vegetates again as soon 

 as ripe. 



Both varieties are best propagated by offsets of the 

 root of moderate size, for if those are employed which 

 the one variety produces on the summit of its steins, 

 they seldom do more than increase in size the first year, 



but are prolific the next ; this also occurs if very small 

 offsets of the root are employed. 



Planting. They may be planted during October . .r 

 November, or as early in the spring as the season will 

 allow, but not later than April. In the west of England, 

 assisted by their genial climate, they plant on the shortcut, 

 and take up on the longest day. They are either to be 

 inserted in drills, or by a blunt dibble, 8 inches apart 

 each way, not buried entirely, but the top of the offset 

 just level with the surface. Mr. Maher, gardener at 

 Arundel Castle, merely places the sets on the surface, 

 covering them with leaf-mould, rotten dung, or other 

 liu'ht compost. The beds they are grown in are better, 

 not more than 4 feet wide, for the convenience of 

 cultivation. 



The practice of earthing over them, when the steins 

 have grown up, is unnatural ; and by so doing the bulbs 

 are blanched, and prevented ripening perfectly, on which 

 their keeping so much depends. So far from following 

 this plan, Mr. Wedgewood, of Betley, recommends the 

 earth always to be cleared awav down to the riim from 

 whence the fibres spring, as soon as the leaves have 

 attained their full size, and begin to be brown at the 

 top, so that a kind of basin is formed round the bulb. 

 As soon as they vegetate, they intimate the number 

 of offsets that will be produced by showing a shoot 

 for each. 



They attain their full growth towards the end of July, 

 and become completely ripe early in September ; for 

 immediate use, they may be taken up as they ripen, 

 but for keeping, a little before they attain perfect 

 maturity. 



POTATO, SWEET or SPANISH. Ipomoc'a Batatas. 



POTENTTLLA. Cinquefoil. (From potens, powerful ; 

 supposed medicinal quality. Nat. ord. Roscworls 

 [Rosaces?]. I.inn. ii-Icosandria, $-Trigynia.) 



Hardy herbaceous perennials. P. ca'ndicans requires 

 protection in the winter ; seeds and division of the 

 plant in spring ; shrubs, by cuttings of ripe wood in 

 the autumn, or by cuttings in summer, under a hand- 

 li^ht ; good, deep, sandy loam. All yellow-flowered, 

 except where otherwise mentioned. 

 P. adsce'ndens (ascending). See P. INCLINATA. 

 arimonioi'dcs (agrimony- like). See P. SERICEA. 

 a'lba (white), . White. May. Europe (Wales). 

 alchemilloi'des (Alchemilla-like). $. White. July, 



August. Pyrenees. 

 ,, alpe'siris (mountain). |. Orange. July. Europe 



(Britain). 

 pyrena'ica (Pyrenean) \. Rich yellow. June to 



September. Pyrenees. 

 ,, ambi'gua (doubtful. Three-toothed Himalayan). \. 



Yellow. June. Himalaya. 1851. 

 ,, angustifo'lia (narrow-leaved). See P. NIVEA. 

 ,, Anseri'na (goose). J. July. Temperate regipns 



(Britain). " Silver weed." 

 ,, apenni'na (Apennine). i. White. May. Apennines. 



1821. 

 arachnoi'dea (spider-web). See P. PENNSYLVANIA 



ARACHNOTDEA. 



,, arge'ntea (silvery-taroMf). i. June. N. temperate 



regions (Britain). " Silvery Cinquefoil." 

 ,, ,, cala'bra (Calabrian). . Yellow. July. Southern 



Italy. 1829. 



,, ,, tcnui'loba (slender-lobed) . $. Yellow. England. 

 argu'ta (acute). 1^-2. Pale yellow. July. N. Amer. 1826. 

 ,, argyrophy'lla (silvery- leaved). 1-2. Yellow. Summer. 



Himalaya. 1840. 

 ., atrosangui'nea (dark-blood-red). 1-2. Dark 



crimson. July. Himalaya. 1822. 

 ,, leucochro' a ( white-surfaced), i-ii. Yellow. July. 

 ,, astraca'nica (Astracan). See P. RECTA. 

 ,, astragali) o'lia (Astragalus-leaved). See P. BIFURCA. 

 ,, a'tro-sangui'nea (dark-bloody). See P. ARGVROPHYLLA 



ATROSANGUINEA. 



,, au'rea (golden). }. Golden- yellow. April, May. 

 Europe. 



,, ,, chrysocra' speda (golden- thick- footed). J. Golden- 

 yellow. 



,, bi'color (two-coloured). See P. NEPALENSIS. 



,, biflo'ra (two-flowered). J. June. Siberia. 1820. 



,, bifu'rca (iorked-leaved). i. June. Siberia. 1773. 



,, subseri'cea (rather-silky). . June. Astracan. 

 1827. 



