PROPAGATION OF TREES AND SHRUBS 7 



plants; 5 or 10 mg./l., 24 hours, or 2 to 5 mg. per gni. talc being enough, 

 for example, for cuttings of heliotrope, Begonia, and Chrysanthemum (49). 



Treatment of Cuttings by the Solution-Immersion Method 



The cuttings, usually iield in bundles by rubber bands, are set with their 

 basal ends in a solution of root-inducing substance (not in metal con- 

 tainers (58)) about one inch deep and there they remain for a number of 

 hours. Solutions of indolebutyric acid (17, 83) and naphthaleneacetic acid 

 can be used three times if within a week and if most evaporation is mean- 

 while prevented, but solutions of indoleactic acid ma}' deteriorate more 

 rapidly (99). 



Cuttings during treatment should be out of direct sunlight but in good 

 light (17, 79, 81). At night or in very dark weather the length of time 

 of treatment may well be somewhat longer (113). 



Moderately dry air and ordinary room temperatures have given good 

 results but the rate of absorption of the chemical varies with humidity and 

 temperature of the air (79) and a shorter treatment in a very warm room 

 may be long enough (125). The temperatuie of the solution itself may 

 also be a factor. Cuttings of Thuja dlccidentalis var. cricoidcs which were 

 taken here in December rooted the same, 64 percent in seven months, 

 whether or not they were treated with indolebutyric acid (25 mg./l., 20 

 hrs.) at 68° F., but when this treatment was applied at an initial temper- 

 ature of 90° F. dropping to 86° F. in one hour and to 68° F. for the fol- 

 lowing 18 hours, they rooted 100 percent in three months. Rooting of 

 similar cuttings of Taxus media and Picca pungcns var. globosa treated for 

 20 hours with solutions of indolebutyric acid was similarly more improved 

 if the first two hours of the treatment were at 86° F., dropping then to 

 68° F., than if they were treated at an approximately constant temperature 

 of 68° F. 



Cuttings are sometimes rinsed in tap water immediately after this treat- 

 ment (17, 68, 117) and that was the practice here. In other instances 

 (16, 57), they have been placed directly in the rooting medium without 

 rinsing. It is probable that the first method is safer with high concentra- 

 tions; perhaps less effective with low concentrations or if length of time 

 of treatment is very short. 



The Powder-dip Method of Treatment as Compared with the 

 Solution-immersion Method 



Treatment by the powder-dip method consists in dipping the basal half 

 inch of cuttings, previously moistened with water (18, 49, 58, 104), in talc 

 with which a root-inducing substance has been intimately mixed in the 

 proportion of a certain number of milligrams per gram (mg./gm.) talc. 

 Talc alone improves the rooting of cuttings of some species (49, 96) but 

 does not improve it enough. The excess of powder is removed by tap- 

 ping the cuttings on the inside of the container of the powder, after which 

 they are inserted in the rooting medium just as if they had not been 

 treated (49). 



The powder-dip method is quick and convenient, therefore popular; 

 but when cuttings are handled in bundles, solution treatments may have 

 some advantage in convenience and thoroughness of application (99). 

 The powder-dip method has, in some cases (18, 114), given results 



