48 



warm weather following a period of rainy weather while the foliage 

 was turgid. The.sulfate solution may have a corrosive action upon 

 the cell walls, since its effect was soon evident upon dead or yellowing 

 tissue, injured tissue, and at the mutilated edges of the leaves. 



In addition to the action upon the leaf tissue, it was found that, 

 within a certain restricted area on Plat 5 (the Robinson lawn) where 

 the solution at one time was applied too liberally, there was a very 

 noticeable effect upon the crowns of the dandelion plants. Upon 

 digging these plants, they were found to show more or less injury in 

 the form of a decay of the upper portion of the crown. Often the 

 decayed layer was one-half inch thick. 



EFFECT OF IRON SULFATE SOLUTION UPON OTHER LAWN WEEDS. 



During the progress of the work opportunity was afforded to 

 observe the effect of the solution upon other lawn weeds. In a 

 general way the results can be briefly stated as follows : 



Common chickweed (Stellaria media) was killed after repeated 

 sprayings. 



Purslane (Portulacca oleraced) and yellow trefoil (Medicago lupu- 

 lina) were killed. 



Wild geranium or cranesbill (Geranium Robertianum) and mallow 

 (Malva rotundifolid) were badly injured. 



Heal all (Prunella vulgaris), gill-over-the-ground (Nepeta heder- 

 acea), broad-leaved plantain (Plantago major), curled dock (Rumex 

 crispus), and narrow-leaved plantain (Plantago lanceolata) were 

 either killed or badly injured. 



Knot grass (Polygonum aviculare) and crab grass (Digitaria humi- 

 fusa) were either uninjured or were slightly injured. 



In the case of some of the weeds listed above, the extent to which 

 they were injured depended upon their age and the thoroness with 

 which they were sprayed. However, it must be remembered that 

 drenching a lawn to kill the weeds may be followed by very severe 

 injury to the grass. 



Experience with lawn weeds such as chickweed, crab grass, dock, 

 plantain and wild geranium emphasized the necessity of reseeding 

 the lawn heavily after the last spraying in order to fill up the bare 

 places in the turf where the clumps of dandelions were killed out. 

 Nature appears to abhor bare places, especially in lawns, and often 

 covers them with weeds. 



