66 EXPERIMENT STATION. [Jan. 



plants and length of internodes were found in those series where 

 the light was less, while, on the other hand, the shortest inter- 

 nodes and greatest diameter of the stems occurred in those 

 plants which received the most light ; hut the average length and 

 width of leaf were variable, as shown in the table. The data 

 giving average length and width of the leaves were obtained 

 by multiplying the width by the length, and represent fairly 

 well the size of the leaf. 



It will be noted that the plants growing where the light was 

 excluded had the largest leaves. The leaf development, of 

 course, varies according to the season, and is also affected by 

 light exposure, methods of pruning, etc., and greenhouse cucum- 

 bers usually have much larger leaves than field cucumbers. 

 Whatever the optimum photosynthetic requirements for cucum- 

 bers may be, or what relationship exists between the size of the 

 leaves and optimum photosynthesis, we do not know; but the 

 production of larger leaves under certain light intensities is 

 apparently a response to a demand for greater carbon assimila- 

 tion. 



To summarize the results of these experiments : burning from 

 hydrocyanic acid gas is more extensive on plants grown under 

 poor light conditions than where the light is good, showing that 

 weak tissue, such as is produced by inferior light, is more sus- 

 ceptible to burning from fumigation. 



Influence of Varying Percentages of Moisture on the 

 Development of Cucumbers and their Suscepti- 

 bility TO Burning from Hydrocyanic Acid Gas. 

 That the percentage of moisture in soil has an important 

 bearing on crop production, exerting a modifying influence on 

 growth and development, is well understood and usually taken 

 into consideration by experimentalists. Plants will make 

 greater growth in a relatively moist soil, although there is an 

 optimum moisture content of the soil for most plants. Besides 

 growing more rapidly, a plant in a moist soil develops a dif- 

 ferent type of tissue, which is usually less resistant to various 

 injurious agencies than the dry soil i^lant. Two or 3 per cent, 

 more water in a plant than what might be considered the nor- 



