ANNUAL REPORT, 1937 31 



this treatment usually improved germination as did also formaldehyde 6 cc. 

 (in 500 cc. water) similarly used. 



Formic acid appears to be a good soil fungicide and its use is now being further 

 investigated. Seven cc. of formic acid (90 percent), diluted to 300 cc. (per sq. ft.) 

 and mixed with the soil immediately before seeding, controlled damping-oflf very 

 well, improved germination of all species with which it was used, and did not 

 interfere with growth. It must, of course, be handled with care to avoid injuring 

 one's skin. 



Work with salicylic acid has been continued, for an application of 6 to 8 gm. 

 per sq. ft. has, in the presence of fungi, usually improved germination; and this 

 material, being a crystalline powder, has the advantage of being readily applied 

 to soil without the necessity of first preparing either a dust mixture or a solution. 



A pyroligneous acid, made from pine wood, was applied to soil at the rate of 

 about 125 cc. per sq. ft., undiluted, immediately before seeding. This satisfactorily 

 controlled damping-off without injury to the species of plants with which it was 

 used, and its use in this way, without the addition of water, is now being studied 

 further. 



Some work has been done on the sterilization of soils, in closed containers, by 

 the vapors of formaldehyde rather than by a solution. Soils so exposed to these 

 vapors, for a few days, could not be used immediately without injury to seeds, 

 but after being aired for two days, there was no injury to growlh and, most fungi 

 having apparently been killed, germination was improved. 



There are soils in the trade which have been sterilized by the firms supplying 

 them and, unless they later become contaminated, there is little or no damping-oflf 

 in them. To lessen the cost of using such soil, the writer has diluted it with 

 washed sand, up to half and half. No increase in damping-oflf resulted; and 

 seedlings, up to that stage at which they are commonly transplanted, grew well 

 without the addition of nutrient. 



Damping-off and Growth of Seedlings and Cuttings of Woody Plants as A f ected 

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

 of the interest of nurserymen in the effects of such growth substances as indole- 

 butyric acid on rooting of cuttings, a paper on some of the writer's results was 

 published in our Nurseryculture Bulletin vol. 2, no. 5 (September 15, 1937) 

 and work along this line has been continued. Special attention is being given 

 to the time of taking cuttings and the relation of season to the response to treat- 

 ment. 



Such treatments are unnecessary for the cuttings of many species which, if taken 

 at appropriate times, root readily enough without treatment. This was true of the 

 following species when cuttings were taken at the times of year mentioned: 

 Viburnum rhylidophyllum Hemsl., Cephalanlhus occidenlalis L., Buddleia Davidi 

 Franch., and Stephanandra incisa Zabel. in the first week of August; Pachistima 

 Canbyi Gray, Coronilla Enterus L., Helianthemum nummularium L., Chamaecy- 

 paris pisifera Endl. var. plumosa Beiss., Thuja occidenlalis L. var. umbraculifera 

 Beiss., and Juniperus Sabina L. var. tamariscifolia Ait. in the third week of 

 October; Cytisus Beanii Nichols., C. purgans Benth. &. Hook., Genista pilosa L., 

 Vaccinium Vitis-Idaea L., and Calluna vulgaris (L.) Hull, in the third week of 

 November; and Juniperus communis L., J. procumbens Sieb., and /. scopulorum 

 Sarg. var. horizontalis D. Hill in the last week of December. 



Some other species and some of the above if taken at other times may root 

 more rapidly if cuttings are treated, but not always in larger percentages finally. 

 This was the effect, for example, of indolebutyric acid on Calluna and Dorycnium 

 hirsutum Ser. It may, in fact, be principally by hastening rooting that such 

 treatments improve the rooting of cuttings of some species, for cuttings which 



