8 
BULLETIIST 821, U. S. DEPAETME:N'T OF AGRICULTURE. 
In order to enable the observers to secure individual- tree performance 
records from as manv as 10 plats it was found necessarv to arrange 
the plats in such order that the smallest possible number of trees 
would give rehable data of the comparative tree and fruit conditions 
in the heated and nonheated orchards. Each plat included a block 
10 trees long by 10 trees wide, or, roughly speaking, an acre of lemon 
trees. On account of the great amount of work which would be 
necessary in securing individual-tree performance records from all 
the trees in the selected plats, it was found necessary to restrict the 
actual detailed records- to not more than 10 trees, and in some cases 
to 5 trees, in each plat. The trees finally used for this study were 
located by taking one of the trees at the center of the block and the 
four trees at the corners. It was thought that by securing the records 
of these trees and then by multiplying the figures obtained by the 
factor 20 a fairly accurate line could be obtained on the production 
of the plat on an acre basis. Where 10 trees were used in securing 
the records two trees were taken in the center of the block and two on 
each corner. In these plats the acre figures were secured by multi- 
plying the total production of the 10 trees by the factor 10. 
After the performance-record trees were located they were care- 
fully studied from the standpoint of strain characteristics, as it was 
desirable that only typical trees of the best strain of the Lisbon and 
Eureka varieties should be used for this study. 
Table II. — Description of the plats selected for the study of the effectiveness of orchard 
heaters for frost protection. 
Plat. 
Variety. 
Treatment. 
Num- 
ber of 
trees. 
Num.- 
berof 
pick- 
ings. 
Picking period. 
Comparativ( 
plats. 
No. 1---. 
No. 2.... 
No. 3..-. 
No. 4.... 
No. 5.... 
No. 6.-.. 
No. 7.... 
No. 8.... 
No. 9.... 
No. 10... 
Lisbon 
...do 
Eureka — 
Lisbon 
Eureka — 
Lisbon 
Eureka — 
Lisbon 
...do 
...do 
Not heated- 
Heated 
Heated 
do 
Not heated. 
Heated 
Not heated. 
19 
Feb. 14 to Dec. 12, 1913.. 
Feb. 15 to Nov. 17, 1913. 
do 
Mar. 3 to Dec. 12, 1913... 
Mar. 4 to Dec. 12, 1913... 
/Mar. 6 to Dec. 8, 1913.... 
\Jan. 3 to Dec. 23, 1914... 
Mar. 7 to Dec. 13, 1913... 
/Mar. 10 to Dec. 18, 1913.. 
\Jan. 31 to Dec. 30, 1914 . . 
Mar. 12 to Dec. 12, 1913.. 
Mar. 14 to Dec. 1,1913... 
4 
3 
5, and 7 
1 
3 and 7 
3 and 5 
1 Plats 2 and 3 were partially protected by heaters in neighboring orchards. 
2 Inadequately heated; one heater for every four trees. 
The position of the plat was adjusted so that the trees finally used 
were, with one exception, of the same strain in all the comparative 
plats. The number of the plat, the variety of lemons, a statement 
of whether the orchards were heated or nonheated, the number of 
trees in each plat, the number of pickings made from the trees, the 
periods during which the pickings were made, and the number of 
plats used for comparison are shown in Table 11. A study of this 
