MISSOURI BOTANICAL GARDEN BULLETIN 31 
and those growing in the country removed from the ill effects 
of smoke, a striking contrast is noted. 
The few evergreens still living in the Missouri Botanical 
Garden apparently make little or no progress from year to 
year, and eventually all will probably succumb. The large 
collection of evergreens set out by Mr. Shaw, such as pines, 
junipers, arbor-vitae, hemlocks, larches, yews, and firs, which 
previously constituted such an attractive element in the land- 
scape, have all disappeared. Broad-leaved evergreens, such 
as rhododendrons, azaleas, hollies, ete., are likewise affected. 
While the American holly is apparently more resistant to the 
injurious action of smoke than any similar tree, its growth 
is nothing like what it should be. 
The effect upon trees which annually shed their leaves is 
not so marked, since, of course, they do not expose through- 
out the year such a large surface to be affected by smoke. 
The fact remains, however, that such trees as the birches, 
beeches, hackberries, alders, sour-gums, hard maples, crab- 
apples, lindens, and black locusts have been almost entirely 
eliminated from places in the city subjected to serious smoke 
trouble. Even the redbud shows the effect, and it is almost 
impossible to bring to bloom satisfactorily at the Garden, 
dogwoods, crab-apples, lilaes, ete. Indeed, nothing is more 
marked than the scarcity, if not entire absence, of flowers 
on some of our most beautiful shrubs when subjected to the 
action of smoke. The golden-bell and bridal-wreath fre- 
quently fail to blossom at all, and weigelias, hydrangeas, 
flowering currants, roses, and a long list of similar shrubs at 
the Garden are increasingly showing the effect of having to 
live in an atmosphere more or less saturated with toxic 
substances. 
Occasionally, we have a real catastrophe at the Garden 
which, because of a peculiar combination of atmospheric con- 
ditions, produces damage in a few hours which ordinarily 
would be spread over a long period of time. In November, 
1917, hundreds of plants in the greenhouses were destroyed 
or seriously injured by the action of one smoke cloud. 
Chrysanthemums, cinerarias, orchids, ferns, azaleas, and 
numerous other plants either dropped their flowers and most 
of their leaves or had the foliage so discolored by the action 
of the smoke that only a small percentage of them survived 
(see November, 1917, Butuerin). Those plants which were 
not annuals, and consequently not thrown away, were so 
