28 MASS. EXPERIMENT STATION BULLETIN 339 



the first application on June 8, and ending with the last on August 24 at the 

 Field Station, Waltham, and on September 21 at Rice's in Lexington, making 

 a total of 10 and 13 applications respectively. The significant results of these 

 tests are as follows: 



Number of infections Average number of 



Plots per 1,000 harvested flowering 



flowering stems stems per plant 



Sprayed Not sprayed Sprayed Not sprayed 



Waltham Field Station 96 1,630 3.48 4.73 



Rice — Lexington 51 2,556 1.65 1.39 



Aside from the good control obtained, the sprayed plants showed better 

 color and growth according to the judgment of the Research Committee of the 

 New England Carnation Growers Association. The tests gave a previously 

 divided sentiment convincing evidence of the virtue and safety of the treatment 

 recommended. 



This project is terminated, but the preparation of manuscript has been de- 

 layed by other work. 



Diseases of Herbaceous Ornamental Plants Caused by Soil-Infesting 

 Fungi. (W. L. Doran.) Seedlings do not often damp-off in washed sand unless 

 the sand is later contaminated, as by inoculation. In five different sands, 

 however, even with potassium nitrate added as nutrient, seedlings of most 

 species used in this work usually grew less well than in soils. Absence of 

 damping-off is not enough if seedlings meanwhile grow but poorly; and sands 

 were not very satisfactory media for seedage of species, the seedlings of which 

 are naturally small and slow to grow in any medium. 



In other experiments, seeds were sowed in other media including sand and 

 sphagnum (half and half) and sand and peat moss (half and half), with the ob- 

 ject of determining the effect not only on germination and damping-off but 

 also, and especially, on growth of seedlings. Growth was better in sand and 

 sphagnum or in sand and peat moss than in sand, and was often as good as in 

 soil, provided that potassium nitrate was added in all cases. 



Growth of seedlings of some species was better in sand and sphagnum than 

 in sand and peat moss. This may be, at least partly, the effect of soil reaction. 

 The addition of peat moss to sand increased acidity more than did sphagnum; 

 for the latter, added to sand, lowered pH values very little or not at all. 



There was sometimes more damping-off in these mixtures, especially in sand 

 and peat moss, than in sand alone; but in them, as in sand, it was usually tri- 

 fling as compared with its severity in soil. 



Considering both damping-off and growth of small, slow-growing seedlings, 

 no medium for seedage gave better results than did sand and sphagnum. 



If soil is used, as it often must be, then soil disinfection is in order, and for 

 this purpose formaldehyde dust has largely replaced the less convenient liquid 

 formaldehyde. On the basis of work here reported upon, acetic acid dust, 

 instead of acetic acid in water, may be similarly used with good results and no 

 less convenience than formaldehyde dust. 



Acetic acid dusts containing 24 to 25 percent acetic acid have been made by 

 absorbing 1 pint of 80 percent acetic acid in 2.5 pounds of powdered wood char- 

 coal, and these were well mixed with moderately dry soils, naturally infested 

 or artificially inoculated, using 1.5 oz. of the dust per square foot of soil (3 inches 

 deep '. Seeds were sowed immediately and soils were then well watered. Good, 

 although not always complete, control of damping-off was thus obtained. 



