MISSOURI BOTANICAL GARDEN BULLETIN 27 
ating gas—in one million parts of air causes the flowers to 
close. Especial care should therefore be taken to prevent as 
much as possible the escape of illuminating gas, whether 
from leaks or careless lighting. Good ventilation will doubt- 
less tend to minimize the injury from poisonous gases, but in 
providing it, it should be remembered that many plants are 
extremely sensitive to sudden chilling. 
Water.—Perhaps no one factor is so important in the 
successful growing of plants in the house as is proper water- 
ing. Owing, however, to the striking differences between 
the various kinds of plants as regards water requirements, 
as well as the differences in temperature, soil, humidity, etc., 
to which plants are subjected in houses, it is practically im- . 
possible to give general directions which will be fundament- 
ally helpful. Practical experience alone, it seems, can teach 
one the proper use of water for house plants. With the ex- 
ception of certain desert plants, like the cacti, most plants 
thrive best in a thoroughly moist soil, and are injured by 
even slight degrees of wilting. It appears, however, that over- 
watering rather than under-watering is the more frequent 
cause of failure. While most plants require a thoroughly 
moist soil, a muddy or water-logged soil is in most cases 
distinctly injurious. Such a condition can be effectively 
avoided by providing ample drainage. But even where 
flower pots provided with drainage openings are used the 
common practice of placing the pots in turn in a jardiniere 
without inage provisions leads to disaster. As water 
drains out at the bottom of the pot, it accumulates in the 
jardiniere, and, if enough is given, may accumulate to such 
an extent as to more than saturate the soil with water. 
Where jardinieres or other vessels without drainage facilities 
are aN 8 great care should be taken to prevent over-watering. 
It is in all cases better to use shallow under pans, since the 
latter will overflow before an injurious amount of water _ac- 
cumulates in the soil, as so frequently occurs where jardin- 
ieres are used. If the latter are desired, a form ic bea 
with shallow under pans and having provision for nage 
should be used. . 
As regards the frequency of watering, again no definite 
recommendation can be made. Usually it 1s not necessary 
to water house plants every day. Best results seem to be 
obtained by oe an 4 waterings at longer intervals. In this 
connection it should be remembered that growing plants 
need a great deal more water than do dormant ones, flower- 
ing plants ially requiring large quantities of water for 
the full develonsiens of blossoms. It is further desirable in 
many plants to spray or even wash the leaves in order to 
