74 MISSOURI BOTANICAL GARDEN BULLETIN 
similarly affected as well. The commercial florists have, 
where possible, removed their producing greenhouses into 
the country to avoid the damaging effects of a smoky atmos- 
phere. 
CITY PLANTING ZONES 
The City Park Department has been forced to discontinue 
its nursery, formerly within the city park area, moving to 
a large tract of land facing the river at Chain-of-Rocks. 
Here a splendid nursery has been established for several 
years, producing sufficient plants to supply not only new 
parks and boulevards but to replace the thousands of plants 
which die annually in the smoke-laden areas. 
Within this last few years, the Park Department, collabo- 
rating with the Garden, has tested numerous trees, shrubs, 
and perennials in various parts of the city for their smoke 
resistance. As a result the entire city has been divided into 
zones and a list made of the various trees and shrubs that 
have survived in these areas. While it is almost impossible 
definitely to outline districts, since they usually merge 
gradually from one to the other, the information obtained 
furnishes a workable basis for general purposes. The worst 
region is No. 3 (see plate 15), and this is to be expected 
since it includes the Mill Creek Valley as well as the crowded 
business district from which volumes of smoke arise, particu- 
larly during the winter. Zone No. 2 is somewhat scattered, 
being in most cases away from the railroads and manu- 
facturing plants, embracing the more or less open tracts set 
aside as parks, including the Garden. The most favorable 
areas for vegetation are: on the north, Bellefontaine and 
Calvary cemeteries; on the northwest, Kingshighway and 
Union Avenue district ; on the southwest, the Clifton Heights 
district ; and on the south, Southampton towards the Gravois 
Road. 
The following lists of plants form a comprehensive basis 
by which amateurs, gardeners, and landscape architects may 
be guided in planning city gardens, especially when con- 
sidering permanent effects. The cross mark signifies that 
the particular plant is recommended for the district indicated 
