74 JOURNAL OF TTTR ROYAL HORTTCnLTURAri SOCIETY. 



and immune to specific diseases. Tliere have been various claims in 

 this direction, and apparently in the U.S.A. several successes. There 

 was a hope that Eriophyes ribis (the black-currant mite) would be 

 conquered in this way, but fruit-growers are still waiting an immune 

 variety. It has been claimed that certain potatos are very resistant to 

 Phytophthora infestans. Unfortunately, experience has taught me that 

 some of those varieties which have been said to be the most resistant 

 have been the first to succumb under certain conditions of soil and 

 climate. 



Twelve years ago I gathered some wild parsnip-seed ; the plants 

 grown therefrom have since been regularly selected and cailtivated in 

 their natural habitat, but under garden conditions, the object being to 

 get a hollow-crown variety, immune to rust. Two years ago I had 

 succeeded in getting a good-shaped plant, although not so large as 

 usually demanded, of excellent flavour and resistant to rust. The next 

 season a still farther improvement in size and flavour was reached, 

 but, alas! rust appeared. Last season's results were very disappoint- 

 ing. I hear, however, from some to whom I gave seed last season, 

 that their results were satisfactory, or largely so. Does this mean 

 that the change of soil and climate invigorated to the extent of making 

 resistant? It may be so. In this connection it may be mentioned that 

 fruit-trees are often attacked badly by fungi on some soils, but are 

 practically immune from their attack on others. Thus, King of the 

 Pippins, Eibston Pippin, Cox's Orange, and several others are attacked 

 badly with canker on the formations of the Thanet sand. Even the 

 common crab-apple is se badly attacked that the cankered stems are 

 sometimes used for ornamental cabinet-work. A few miles away, 

 where the soil is very shallow and rests directly upon the chalk, not- 

 withstanding hundreds of acres of apples, including those mentioned, 

 are grown, a cankered tree is rarely seen. Cox's Orange, and especially 

 Peasgood's Nonesuch, do extremely well at Swanley, but a few miles 

 nearer Eochester not nearly so well. Farmers know that a judicious 

 rotation is no small means of keeping plants healthy. The difficulty 

 which gardeners have of thoroughly purifying the glasshouse soil is well 

 known to be one about which they would heartily welcome sound advice, 

 and it is to be hoped that experimental work now in progress w^ll be 

 productive of satisfactory results. 



Is it that some soils are so completely adapted to particular plants 

 that they invigorate to the extent of making disease resistant, or is it 

 that a something is absorbed by or formed in the plant which is toxic 

 to the pest? In 1908 I had a heap of London manure adjoining a 

 potato field. On that heap came up several self-sown potatos and 

 tomatos. The potatos in the field w^ere badly infected by Phytophthora ; 

 those on the manure heap remained vigorous a much longer time, 

 and the tomatos also went on fruiting. This is precisely the reverse 

 of what was expected. Was it something taken from the manure that 

 protected them from attack? Considered in conjunction with other 

 experiences, I rather believe so. It is such problems that one would 



