THE PEACH AND NECTARINE. 



513 



seared with adhesion. For gum and canker 

 abundance of remedies have been prescribed ; 

 as both are, however, generally occasioned by 

 being bruised or wounded in some way or other, 

 and not unfrequently by injudicious pruning, 

 and probably often by being planted in a wet 

 uncongenial soil, the best remedy is to avoid 

 as much as possible these causes. In regard to 

 mildew, some sorts are more liable to its attacks 

 than others, such as the Royal George, Royal 

 Charlotte, &c. The appearance of this inveterate 

 enemy, and also of its congeners, was attributed 

 by Mr Knight to a derangement in the foliage, 

 caused by the leaves absorbing an excess of 

 moisture from the atmosphere under certain 

 conditions. " It has long appeared to me," he 

 says (in " Horticultural Transactions," vol. i. 

 p. 86), "to be the want of a sufficient supply of 

 moisture from the soil, with excess of humidity 

 in the air, particularly if the plants be exposed 

 to a temperature below that to which they have 

 been accustomed. If damp and cold weather 

 in July succeed that which has been warm and 

 bright, without the intervention of sufficient 

 rain to moisten the ground to some depth, the 

 wheat crop is in general much injured by mil- 

 dew. I suspect," he says, " that in such cases 

 an injurious absorption of moisture by the leaves 

 and stems of the plants takes place ; and I have 

 proved that, under similar circumstances, much 

 water will be absorbed by the leaves of trees, 

 and carried downwards through their alburnous 

 substance, though it is certainly through this 

 substance that the sap rises under ordinary cir- 

 cumstances. If a branch be taken from a tree 

 when its leaves are mature, and one leaf be kept 

 constantly wet, that leaf will absorb moisture, 

 and supply another leaf below it upon the 

 branch, even although all communication be- 

 tween them through the bark be intercepted; 

 and if a similar absorption takes place in the 

 straws of wheat, or the stems of other plants, 

 and a retrograde motion of the fluids be pro- 

 duced, I conceive that the ascent of the true 

 sap or organisable matter into the seed-vessels 

 must be retarded, and that it may become the 

 food of the parasitical plants, which then only 

 may grow luxuriant and injurious." Few plants 

 are exempt from its attacks, although some — 

 such as the peach, vine, rose, pea, hop, &c. — 

 are more liable to be seriously injured by it than 

 others. It is not at all improbable but that every 

 species of plant has its own peculiar species of 

 both vegetable and animal parasites, although 

 the same species may not unfrequently be found 

 on different plants ; but in general they are 

 found in greater abundance on the plants to 

 which they appear to have some affinity. Thus 

 we have the Erysiphe communis, the mildew of 

 the pea, the Botrytis efusa on the spinach, the 

 Acrosporium monilioides and Botrytis destructor 

 on the onion, All oidium berberides on the ber- 

 berry, Cylihdrosporium concentricum on the cab- 

 bage, and the recently discovered Oidium 

 Tuckeri, so destructive to the vine, and Oidium 

 crysiphoides, the mildew of the peach. That 

 the various species of mildew are composed 

 of innumerable myriads of very minute fungi 

 is, we believe, admitted on all hands ; there 



appears, however, to be as yet some diversity of 

 opinion as to their origin. Desaisne and Leveille, 

 eminent French naturalists, assert that mildew 

 always originates on the external surface of the 

 plants, and that only on subjects whose tissue 

 is in a previously diseased state. The majority 

 of British cryptogamists equally assert that it is 

 first developed within the tissues, and that it 

 afterwards makes its way through the stomata. 

 The roots of the minute species of fungi, which 

 constitute what is usually called mildew, pene- 

 trate the pores of the epideymis of the leaves, 

 and sometimes the very young wood of plants, 

 as exemplified in the case of the peach ; to sup- 

 port themselves they exhaust the plant on which 

 they grow, by robbing it of its juices and inter- 

 cepting its respiration. " Every specimen of 

 these fungi," says the compiler of " The Cottage 

 Gardener's Dictionary," " emits annually myriads 

 of minute seeds, and these are wafted over the 

 soil by every wind, vegetating and reproducing 

 seed, if they have happened to be deposited in 

 a favourable place, or remaining until the fol- 

 lowing spring without germinating. These 

 fungi have the power of spreading also, by stool- 

 ing or throwing out offsets. They are never 

 absent from a soil, and at some period of its 

 growth are annually to be found upon the plants 

 liable to their inroads." There are no doubt 

 particular states of the atmosphere more favour- 

 able to the appearance of mildew than others ; 

 for it has been generally observed to make its 

 appearance more in a dry than in a moist 

 state, which leads some to suppose that the dry 

 air, acting upon the delicate surface of vegetable 

 tissue, is favourable to its existence. Practically, 

 we find its attacks on the peach and other fruit 

 trees more severe in dry springs than in those 

 that are more genial and humid — on turnips, 

 in dry summers and autumns, than in those that 

 may be considered even wet — in dry localities 

 more than in those where abundance of rain 

 falls. These opinions are somewhat strengthened 

 by the well-known fact, that on wall-trees kept 

 thoroughly syringed with clear water, and on 

 crops of pease and turnips repeatedly watered, 

 mildew seldom makes its appearance. Applying 

 clear water copiously during dry weather, and 

 with considerable force, by a syringe or small 

 garden-engine, will, in a great degree, prevent 

 its appearance ; should it, however, make head, 

 powdered sulphur applied upon its first appear- 

 ance will completely subdue it ; and as a pre- 

 cautionary measure the peach trees should 

 be sulphurated even before its appearance. 

 How the sulphur acts has not as yet been 

 very satisfactorily explained. As it is insolu- 

 ble in water, there can be no advantage in 

 following the general rule of syringing with 

 water in which sulphur has been steeped, un- 

 less the crude particles are held in suspension, 

 so as to be distributed equally over the leaves 

 and young shoots which are the parts affected. 

 The fumes of black sulphur are found a com- 

 plete remedy, but require to be most carefully 

 applied, else the remedy would become worse 

 than the disease. Mons. Grison has suggested 

 the application of hydro-sulphate of lime, which 

 is obtained simply by boiling 1 lb. of flour of 



