DROPSY OF TOMATO. 179 
of needed light. By a process known as transpiration, 
plants are relieved of much water when well lighted, 
but in poor light, since the roots are absorbing water, it 
is apt to accumulate to excess. Well lighted parts of the 
house, then, should be selected for the tomatoes. 
‘“2. Too much water in the soil. Water in excess can 
be withheld from the soil and prevent the trouble, and yet 
provide enough for the plants to grow. 
‘“3. The temperature of the soil may be too near that 
of the air. A high temperature of the soil makes the 
roots active, and if the temperature of the air is not con- 
siderably higher an excess of water is apt to accumulate 
in the plant. The aim would be, then, to have the tem- 
perature of the air considerably higher than that of the 
roots. 
“Lack of proper light also brings about the following 
harmful conditions : 
“1, Acids in the plant accumulate in the dark, and in 
strong light they decrease. When there is an abundance 
of water in the plant these acids draw large quantities 
into the cells, causing the cells to swell, resulting many 
times in cedema, or in the killing of the protoplasm, so 
that these parts of the plant die and become brown or 
black. 
“2. Lack of light causes weak cell walls. It is only 
when well lighted that plants are capable of making sub- 
stances to build up cell walls with. Therefore, lack of 
light not only favors the accumulation of water, if other 
things are favorable, but it prevents the plants from build- 
ing up strong tissues. In such cases plants can grow 
themselves to death. Possibly artificial light might be 
used to advantage. 
‘““A quiet and close atmosphere also favors the ac- 
cumulation of water in the plant. Good ventilation 
should then be secured. Some means for the artificial 
agitation or exchange of the air at night might probably 
be profitably devised. 
13 FORC. 
