18 BULLETIN 813, U. S. DEPARTMENT OF AGRICULTURE . 
tips. The characteristically pointed shape of the leaves often assists 
in the identification of the trees of this strain. 
One of the very important tree characteristics of this strain is the 
large number of imperfect flowers produced. Usually the blooms 
are very abundant, but most of them fall from the trees. Investiga- 
tion of this condition established the fact that many of the flowers 
are imperfectly developed. Usually the pistils in these imperfect 
flowers are either rudimentary or absent, as shown in figure 4, B 
and C. In either case the flowers fall from the trees soon after open- 
ing. Furthermore, the anthers of the perfect flowers have frequently 
been found to contain Yery little or no pollen. The pollen grains in 
many instances apparently have such a low vitality that they either 
do not germinate or, after germinating, they do not complete the 
processes of fecundation. For this reason the fruits of this strain 
usually have but few seeds. The imperfect development of the flowers 
probably accounts in part for the low production of the trees of this 
strain, and this characteristic is one by which the trees can frequently 
be identified. 
The fruits borne by the trees of this strain, as shown in Plate II 
are usually oblong, longer than is the case with fruits of the Eureka 
strain, of large size, coarse and rough in texture, with a strong ten- 
dency to ridging. The rind is normally very thick. The rag is 
coarse and very abundant; the juice is scant, sometimes being almost 
entirety absent, poor in quality and lacking in acidity; and the seeds 
average less than two per fruit. The fruits of this inferior strain are 
distinctly detrimental in every way to the crops in which they occur. 
Tree-census studies in the Eureka lemon orchards in southern 
California have shown that the number of trees of the Shade-Tree 
strain varies from 10 to 70 per cent. On the average. 25 per cent 
of the trees in these orchards were found to be of this strain. These 
trees, owing to their vigorous vegetative condition, are well adapted 
to top-working. Performance-record studies of such top-worked 
trees have shown that under favorable climatic and cultural conditions 
they can be brought to profitable production of good fruit within 
three years. 
The Shade-Tree strain is one of the most important in the Eureka 
variety, from the fact that the trees, flowers, and fruits have unmis- 
takable characteristics and also owing to its extensive occurrence 
in many Eureka orchards. Its elimination in established orchards, 
through top-working with selected buds from trees of the Eureka 
strain, will increase and improve the production in many orchards 
not less than 25 per cent. Its propagation in the future can be 
avoided largely through bud selection from superior performance- 
record trees of the Eureka strain. 
