PROPAGATION OF TREES AND SHRUBS 11 



50 mg./l. in 2.5 percent sugar solution than by this concentration of the 

 acid in water. Similar cuttings of Taxus media rooted in equally large percent- 

 ages after treatment for 17 hours with indolebutyric acid 100 mg./l. in wa- 

 ter and in the sugar solution, but cuttings given the latter treatment had 

 better roots. Rooting of cuttings of two varieties of arbor-vitae and three 

 varieties of Norway spruce, however, was no better after treatment with 

 solutions containing both sugar (2.5 percent) and indolebutyric acid than 

 after treatment with a solution of indolebutyric acid only. 



Acetic Acid 

 Vinegar or dilute acetic acid has long been recommended in horticul- 

 tural literature as a treatment for cuttings or rooting media. It may have 

 somewhat improved the rooting of cuttings of some species but, if so, the 

 improvement was probably slight compared with that which, with some 

 species, results from the use of such growth substances as indolebutyric 

 acid (3); and in the work of other investigators (48, 113), acetic acid 

 has been totally inefifective. 



Rooting Media 



Sand or a mixture of sand and peat moss are most commonly used. 

 The latter, referred to as sand-peat, sometimes consists of equal parts of 

 sand and peat moss, but it gave better results and was usually made and 

 used here in the proportion of sand two parts (by volume, in all cases) 

 and peat moss one part. There is probably no better rooting medium 

 than sand-peat for cuttings of ericaceous plants, although, for some 

 species, their native soil may be as good, and sand-peat is a better rooting 

 medium than sand for cuttings of the majority of woody plants (58). But 

 softwood cuttings of many species, including a number of those named 

 below, have rooted better in sand than in sand-peat. 



German peat moss is now practically unobtainable. Some native peats 

 will do as well, but, lacking both, more use might well be made of sandy 

 soil. Sandy soil, a mixture of sand two parts and sifted loam one part, 

 is a good rooting medium for cuttings of some, not all, species of woody 

 plants (27). It is also sometimes used as a rooting medium for cuttings 

 of some herbaceous plants, but the risk of attack by soil fungi in that 

 medium, unsterilized, might be greater with them than with cuttings of 

 woody plants and only the latter are here considered. 



The good effect of loam in a rooting mixture (27) may be due to the 

 presence of indoleacetic acid (34) or other root-inducing substance. Soil 

 fungi in an organic medium are known to produce auxin (86), and the 

 reaction of plants to applied hormones was less marked in good soil than 

 in sand (34). Nutrients in loam may also be a f?.v.tor. Their application 

 to sand improved the rooting of cuttings of Norway spruce (36) and a 

 honeysuckle (40). It is possible too that vitamins are involved. Cut- 

 tings of Asiatic sweet-leaf and Pfitzer juniper rooted better in the sandy 

 soil which was used here than they did in sand and these are both species 

 the cuttings of which responded to applications of vitamins to sand 

 (98, 103). 



It should be noted, in this connection, that Vitamin Bi has had little 

 if any effect on the rooting of cuttings not previously treated with a root- 

 inducing substance (103, 109, 114), and that treatment of cuttings with 

 Vitamin Bi after their treatment with a root-inducing substance did not 



