128 Agkicitltural Expkkiment Station, Ithaca, N Y. 



1. Insufficient light. The long nights of the early winter months, 

 numerous cloudj^ days, and in part, the walls and framing of the forc- 

 ing house, deprive the plants 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 temper- 

 ature of the air is not considerably higher an excess of water is apt to 

 accumulate in the plant. The aim would be then to have the tempera- 

 ture 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 p)lant 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 oedema, or in the killing of the proto- 

 plasm 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 substances 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 

 building up strong tissues. In such cases plants C2iX\ grow themselves to 

 death. Possibly artificial light might be used to advantage. 



A quiet and close atmosphere also favors the accumulation 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. 



Varieties of tomatoes more subject to the oedema. Those with a 



tendency to a very rapid and succulent growth are more liable to the 



trouble. Tomatoes which develop a firm woody young stem are less 



liable to it. 



GEO. F. ATKINSON. 



