18 BULLETIISr 813, U. S. DEPAKTMENT 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 very 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 

 entirely 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. 



