10 BULLETIN" 1477, U. S. DEPARTMENT OF AGKICULTURE 
the domestica varieties, although in these varieties there is consider- 
able divergence in the extent of growth and manner of performance 
of the spurs. Some varieties, including the Giant, Grand Duke, 
Pond, Washington, and Yellow Egg, produce few typical fruit spurs 
if the twig is sufficiently vigorous to make a thrifty new growth and 
to produce large-sized fruit, as all new growth forms twigs or dies 
after bearing fruit. In another group of domestica varieties, includ- 
ing the Imperial Epineuse, President, Sergeant, Clyman, and Jef- 
ferson, the spurs make but little terminal growth but often branch 
freely and remain vigorous over a period of years. The Tragedy 
may be included in this group also, though a tendency to produce 
both twigs and spurs is more characteristic of this variety than of 
any other. 
The behavior of the Sweetheart, a little-known variety, illustrates 
a tendency distinct from those just mentioned in that numerous short, 
thrifty twigs grow from the framework and fruiting branches, and 
on these grow numerous lateral twiglike spurs (see pi. 39, C). This 
fruiting wood remains thrifty for a number of years, although but 
little annual growth is made by either the main twig or its lateral 
branches when compared with the twig growth of typically twig- 
forming varieties. The growth is longer, however, than that of spurs 
on spur- forming varieties. 
The Japanese varieties and those derived from them are inclined 
to produce spurs and retain them over a considerable period of years, 
whereas with the domestica varieties the spur-producing tendency 
differs decidedly and the spur development is greatly influenced by 
cultural and climatic conditions. If conditions are unfavorable for 
wood growth, the varieties of the domestica group, which are inclined 
to produce twigs, develop spurs instead, through the failure of the 
twigs to make their normal length growth, although the twigs which 
h&ve terminated in spurs will continue their length growth when 
favorable growing conditions recur. Those varieties which produce 
both twigs and spurs, such as the Tragedy, produce only spurs under 
unfavorable conditions ; but the President, a spur-producing variety, 
will develop fewer than the normal number of spurs under unfa- 
vorable growing conditions, and many of those which are formed 
die after producing fruit (see pi. 31, D, and pi. 37, B). 
The varieties which normally produce spurs, rather than twigs, 
form the spurs along the greater part of the length of all 1-year-old 
branches except on the small slender shoots and a segment at the 
base of the large shoots. Where, on account of the lack of soil mois- 
ture or for other causes, trees of the domestica group make little 
growth and all new shoots are small, few, if any, spurs are formed 
along them. This result is much less striking with varieties of the 
Japanese group. With the domestica varieties where the conditions 
for wood growth are unfavorable and the new shoots are short, 
fruit is borne at almost all nodes of the 1-year-old wood except near 
the tip, and spurs are rarely produced at the fruiting nodes (see pi. 
32, A). This leaves the fruiting nodes barren after the fruit ripens. 
On the whole, a greater portion of the crop is borne on 1-year-old 
wood in the clomestica group than in the Japanese, since many domes- 
tica varieties produce most of their fruit on this wood; but the 
