28 MASS. EXPERIMENT STATION BULLETIN '22(i. 



Top Varieties Root A'arieties 



Red Astrachan Own rooted 



Mcintosh Ben Davis 



Yellow Transparent Boug-li (Sweet) 



Baldwin Northern Spy 



AVagener Red Astrachan 



Tolnian Wagener 



Wealthy 



Oldenhurg (Duchess) 

 Yellow Transparent 

 English Paradise 



The balance of the orchard consists of various other varieties on a num- 

 ber of diflferent stocks. 



The growth of the trees has already given us some striking results. 

 Figure 1 shows the average trunk diameter in 1924. of the six main 

 varieties on ten different stocks. 



The first thing noticeable in this figure is the larger growth of Lhc 

 own rooted trees of the more vigorous varieties, — Red Astrachan, Mcin- 

 tosh and Baldwin. Special attention is called to Mcintosh on its own 

 roots, which is much superior to Mcintosh on any other root. See Fig. 3, 

 Plate I. 



In contrast to the good growth of the own rooted trees, notice the 

 very poor growth of all varieties on Oldenburg roots. This poor growth 

 has been consistent throughout the experiment. It is probably due almost 

 entirely to a lack of vigor of the stock although incompatibility of stock 

 and scion may have had some influence also. Fig. 4, Plate I, shows a 

 Mcintosh tree on Oldenburg roots. Compare this with Fig. 3, Plate I. 



The Northern Spy has always been considered a desirable stock in 

 this country where it has been grown on seedling roots and then used 

 for top-working. In South Africa and Australia where it has been used 

 as a root stock to resist the attacks of woolly aphis, it is considered a 

 dwarfing stock. In Fig. 1 it shows up as being fairly vigorous. Trees 

 on this stock grew much more vigorously in 1923 and 192i than pre- 

 \iously: The weak growth of trees on Northern Spy during the first few 

 \ears was probably due to Hairy Root, a form of Crown Gall with 

 which most Northern Spy stock was infected. It is probable that the 

 Northern Spy is a vigorous stock after it has grown sufficiently to over- 

 come the effects of Hairy Root. 



Crown Gall is not confined to the Spy stocks. Most of the others 

 are infected more or less with some form of it. Data will he collected 

 later to determine how much it has affected the results. 



The Bough stocks show up in Fig. 1 rather better than the Northern Spy 

 stocks. Tills difference will probably be reversed in the next few years. 

 as the Bough stocks have behaved just the reverse of the Northern 

 Spy. They were the easiest to root of any of the stocks and grew so 

 well the first few years that they got a big start over most of the 

 others. But the past two or three years the trees on Bough stocks have 

 been slowing down in their growth as compared with those on most of 

 the other stocks. 



Tolman trees on their own roots are really not as poor, after they gei- 



