SET 



542 



S H A 



SETS are the tubers, or portions of I " The length of these rolls at Sion 

 tubers, employed for propngating tube- I House is between fifty and sixty feet, 

 rous-rooted plants. It may be accepted ; but we have no doubt they might be 

 as a rule universally applicable to them, ] made longer, since this depends on the 

 that a moderately-sized whole tuber is ] diameter of the pole or rod, a, and the 

 always to be preferred to a cutting of a \ toughness of the timber employed, or 

 tuber. The latter are invariably morel its power to resist torsion. On one end 

 subject to failure, but if employed, it is ' of this rod, and not on both, as is usual, 

 a good plan to roll them in gypsum i a ratchet wheel, 6, is fixed, with a plate 

 powder. This checks the escape of! against it, c, so as to form a pulley 



their sap, and is friendly to vegetation 

 SEYMERIA. Two species. Hardy 



annuals. Seeds. Peaty soil. 



SHADING deserves more attention 



tlian it usually obtains, for there is not 

 plant when in blossom that is not pro- 



groove between, d, to which a cord is 

 fastened, and about three inches further 

 on the rod is fixed a third iron wheel, 

 about six inches in diameter, and half 

 an inch thick, e. This last wheel runs 

 an iron groove, /, which extends 



longed in beauty and vigour by being along the end rafter or end wall of the 



shaded from the midday sun. Nor 

 should shading be attended to merely 



roof to be covered. 



" The canvas or netting being sewed 



with regard to blooming plants; for I together of a sufficient size to cover the 

 they are benefited by it during all roof, one side of it is nailed to a slip of 

 periods of their growth. Every plant ! wood placed against the back wall, that 

 transpires at a rate great in proportion ! is, along the upper ends of the sashes; 

 to the elevation of the temperature : the other side is nailed to the rod, a. 



the greater the transpiration the more 

 abundant is the absorption of moisture; 

 and the moment the roots fail in afford- 

 ing a supply equivalent to the transpi- 

 ration, the leaves flag, or become ex- 

 hausted of moisture, and if this be 

 repeated often, decay altogether. 



When the canvas is rolled up, it is held 

 in its place under a coping, g, by a 

 ratchet, h, and when it is let down, the 

 cord, i, of the roll is loosened with one 

 hand, and the ratchet cord, k, pulled 

 with the other, when the canvas un- 

 rolls with its own weight. The process 



Shades, properly managed, prevent of pulling it up again needs not be de 

 this injurious exhaustion. Those used j scribed. The most valuable part of 

 at Sion House deserve particular atten- ' the plan is, that the roll of canvas, 

 tion, not only because they are appli- I throughout its whole length, winds up 

 cable to hot-houses, pits, and hot-beds j and lets down without a single wrinkle, 

 of every description, but because they ' notwithstanding the pulley-wheel is 

 may be rendered available in the cover- only on one side. This is owing to 

 ing of fruit walls, to exclude the frost ! the weight of the rod, and its equal 

 from the blossom, and the birds or flies ' diameter throughout. By this plan a 

 from ripe fruit; and also in the cover- | house 100 or 150 feet long, might be 

 ing of flower beds, hay ricks, harvested ' covered with two rolls, the two pulleys 

 corn, temporary structures for public I working at the two ends; but if it were 



assemblages, &c 

 Fig 



thought necessary, the two rods might 

 be joined in the middle, and by a little 

 contrivance, the pulley and groove 

 placed there, so as to work both of the 

 rolls at once from the inside of the 

 house, from the back shed, or from the 

 front." — Gard. Mag. 



SHALLOT. See Eschalot. 



SHANKING is the technical term 

 for a gangrene which attacks the foot- 

 stalks of grapes and the stems of cab- 

 bages which have vegetated through 

 the winter. The shanking of the grape 

 appears to be occasioned by the tem- 

 perature of the soil being too much 

 below that in which the branches are 

 vegetating ; and, consequently, the sup- 



