ANNUAL REPORT, 1938 29 



which should be ferrous sulfate (copperas) with the formula (FeS04. 7H2O). 

 Demonstration of methods and technique and the supplying of information have 

 been services rendered in connection with an increasing interest in this subject. 



Top and Bottom Watering of Plants in Clay Pots. (L. H. Jones.) Tests show 

 that plants in clay pots on a moist surface should be watered on top. Plants 

 deriving their moisture solely from the moist surface under the pot either died or 

 failed to grow. Plants in clay pots kept on a dry surface and watered on top made 

 mediocre growth, with small leaves and short internodes. The practice of stand- 

 ing potted plants in a pool of water for a short time is effective but risky, as the 

 soil may become waterlogged. Water should never be applied, if the soil is 

 already wet to the touch. 



Study of Diseases of Ornamental Herbaceous Plants Caused by Soil-Infesting 

 Organisms, with Particular Attention to Control Measures, (W. L. Doran.) 

 After sowing small seeds, it is a good practice to water the soil from below by 

 setting the containers into shallow pans of water and removing them as soon as 

 the soil becomes saturated. A soil fungicide may be applied at the same time. 

 Both formaldehyde and pyroligneous acid controlled damping-ofT and improved 

 germination when applied in this way, but the latter was less effective. 



When the soil has been previously disinfected by chemicals, however, it may be 

 less safe to water it from below than to water it from above in the usual way. 

 Water generously applied from above may remove some of the chemical from the 

 soil, but this does not happen to the same extent when soil is watered from below. 



Undiluted pyroligneous acid, 175 cc. per square foot, worked into the soil 

 before seeding, gave satisfactory control of damping-off and markedly improved 

 germination and final stands of some species, but 200 cc. proved injurious. More 

 use might well be made of pyroligneous acid as a soil disinfectant by those near 

 enough to its points of manufacture to keep down the cost of freight, for of course 

 it contains much more water than does, for example, commercial formaldehyde. 



Formic acid dusts containing 8 or 9 cc. of the acid per square foot, worked 

 into soil immediately before seeding, gave fair control of damping-oflf and im- 

 proved germination and final stands of some species without injury to growth. 



Crucifers were more susceptible to injury by salicylic acid than were most 

 other plants, and it does not now appear that this material can safely be used 

 with them, although there are continued indications that it may have a place in 

 the protection of some other species against damping-ofif. 



Copper oxalate, in soil applications which were safe enough with slowly germin- 

 ating seeds of some woody plants, was injurious to seeds of herbaceous plants 

 which germinate rapidly. 



A paper on work done under this project was published during the year as 

 Massachusetts Agricultural Experiment Station Bulletin 351. 



Damping-off and Growth of Seedlings and Cuttings of Woody Plants as Affected 

 by Soil Treatments and Modifications of Environment. (W. L. Doran.) Red 

 copper oxide, applied to the seeds of several species, did not satisfactorily protect 

 them against damping-off. Sulfuric acid, applied at the rate of 10 to 12 gm. per 

 square foot of soil, improved the germination of seven species of Rhododendron. 



Untreated softwood cuttings of some species rooted better in a sandy soil, 

 even when it was infested with damping-ofT fungi, than in clean sand, and re- 

 ceived more benefit from growth substances when grown in soil than in sand. 

 However, some species rooted well in sand, and others rooted better in a sand- 

 peat mixture than in soil, whether treated or not. Growth substances did not 

 improve the rooting of leafless hardwood cuttings of deciduous-leaved plants, and 

 generally failed to induce rooting of softwood cuttings of species which did not 



