4 
COLORADO EXPERIMENT STATION 
plum trees top-worked to peach with perfect unions and the ten- 
year-old tops bearing excellent crops of fruit. In this case, the com¬ 
bination seemed to result in a dwarfing of the peach top, though the 
growth is by no means stunted. So in practice, we stick largely to 
the intergrafting of different varieties of the same kind of fruit. 
To understand the principles underlying graftage, the orchardist 
should know how the stems of our fruit trees grow. He should un¬ 
derstand that growth in diameter only takes place in a very small 
region between the bark and sap-wood. This part of the stem is 
called the cambium. In this thin layer of tissue the cells are still 
active and capable of diversion while the activity of each succeeding 
layer, on either side, grows less and less. 
When the limb is split to insert a cion the 
cleft does not grow together along its entire length, 
as some may think. The cells in the cambium layer 
may produce a growth that may, to a certain extent, 
fill up the cleft and cover over the stub but the 
tissues of the stock and cion only make a true union 
where the cells of the cambium layers of the two 
come in contact. Fig. i is a pen drawing of a 
section through a stub grafted two years before. 
The stub was kerf-grafted and shows that no union 
has taken place between the woody tissues of the 
stock and cion. 
The important point in grafting is to see that 
the cambium layers of the stock and cion are 
matched at some point. 
When growth is active we say the bark “peals.” 
Budding is done during this period, not only because 
the ease with which the bark separates from the 
wood simplifies the work of inserting the bud, 
but as growth is more active, the tissues of the bud 
and the stock are more likely to unite. 
TOP-WORKING OLD TREES 
In the working overof old trees it is well to bear in mind that 
trees which show a poor growth in the orchard are seldom worth 
the time it takes to graft them. This is very often true in the case 
of some varieties of apple. For instance, I have never yet seen a 
yellow Transparent stock grow a top worth the space it occupied. 
The same is almost invariably true of tops on Wagner, Duchess, 
Missouri (Pippin), Wealthy and Hyslop crab. In fact, it seldom 
pays to top-work any crab. Figs. 2, 3 and 4 are from a series of 
photographs of a Transcendent crab apple tree, the first showing 
some grafts one year old and some just set; the second figure, the 
same tree one year later (quite a promising tree) ; and the third 
figure the result at the end of the third season, almost the entire 
top blown off by a heavy wind. The grafts were Winesap and 
were sent in a kerf, not a cleft. As a rule the weaker growing var- 
ities are verv unsatisfactory stocks upon which to work other kinds. 
