47 



were cut off below the crown and a small quantity of gasoline applied 

 to the cut surface of the root was used with some success. This 

 proved to be slow and expensive work when attempted on anything 

 like a large scale. 



The results of the work with these herbicides left but one conclu- 

 sion, namely, that they are fairly effective, but the cost of application 

 in time and material is relatively great. When a large number of 

 dandelions are present in a lawn, the injury to the turf by the killing 

 of the grass around each plant may be considerable in the aggregate. 



OBSERVATIONS BEARING ON THE ACTION OF IRON 



SULFATE UPON THE LEAVES AND ROOTS OF 



DANDELION PLANTS. 



At the outset, it was recognized that the action of the iron sulfate 

 upon the dandelion foliage is a separate physiological problem requir- 

 ing considerable study for its solution. This was not attempted in 

 connection with the spraying experiments. However, some obser- 

 vations were made which are herewith presented. Soon after the 

 solution was applied and the foliage began to dry off, the iron sulfate 

 appeared on the plants as a whitish deposit. This was followed by 

 the appearance of small drops of milky juice (latex) on the leaves and 

 flower stalks. Longyear (1918) has recently suggested that this 

 oozing of the latex is due to the absorption of the iron salt by the 

 cells of the leaves and flower stalks, and the production of sufficient 

 internal pressure or turgor to rupture the cell walls and liberate the 

 latex. The writer's views accord with this explanation of the phe- 

 nomenon. Shortly following the oozing of the latex, the foliage 

 begins to blacken, first at the edges of the leaves and around points 

 of injury. This blackening was invariably hastened by bright sun- 

 light. However, it was noted in two cases that the killing of the 

 plants was hastened by a period of cloudy, showery weather following 

 the application of the sulfate in bright sunlight. Also, by heavy dew 

 or a light shower during the first night after spraying. In addition 

 to the withdrawal of moisture from the dandelion leaves there was 

 plainly a chemical action of the iron sulfate upon the chlorophyll of 

 the leaf whereby it was decomposed into a dark-colored substance 

 scattered thru and within the leaf tissue. This action was observed 

 to be more rapid when the application of the spray was made dur.ing 



