6 MASS. EXPERIMENT STATION BULLETIN 382 



Korolkowii (83) and mountain laurel (88), rooting of cuttings of which was 

 more improved by indoleacetic acid. 



Indolebutyric acid is also probably more effective than alpha-naphtha- 

 leneacetic acid for cuttings of most species (16, 25, 43, 48, 83, 114). Ex- 

 ceptions include oriental bittersweet (48), black locust (99), Deutcia scabra 

 (34), Loniccra nitida, cherry plum (82), and species of privet (49) and yew 

 (58), cuttings of which responded more to treatments witli naphthalene- 

 acetic acid. 



Naphthaleneacetic acid is probably more effective with most species 

 than indoleacetic acid (48, 49), although the reverse was true with 

 Kerria japonica (113). Naphthaleneacetic acid, at a given concentration, is 

 more toxic to cuttings of most species than is either of the other two 

 (96, 97). 



Naphthylacetamide and naplithylthioacetamide are less toxic than the 

 above-named acids and are fully as effective root-inducing substances with 

 cuttings of some species (97), although with cuttings of some other species, 

 more difficult to root, indolelnityric acid gave better results (104). 



Preparation of Solutions of Root-inducing Substances 



Solutions, ready for use, are made by dissolving the crystals (previously 

 weighed by the propagator or by a druggist) in a few drops of 95 percent 

 ethyl alcohol which is then diluted with the required amount of water. 

 Naphthaleneacetic acid is difficult to dissolve and may require a period of 

 48 hours in water, with occasional shaking, to get it all into solution (113), 

 but there is no such delay with indolebutyric acid. 



Stock solutions of indolebutyric acid may be prepared for later dilution 

 and, if stored out of the light and in a cool place (16, 88), will keep for 

 weeks (68, 113) without much or any loss in effectiveness. A stock 

 solution which contains indolebutyric acid 200 mg. per liter may, by re- 

 peated dilution with equal volumes of water, be reduced to an indole- 

 butyric acid content of 100, 50, 25 or 12.5 mg. per liter (mg./l., as here- 

 after referred to). Another method (16, 22) consists in dissolving 1 gm. 

 of the crystals in a little 95 percent alcohol, 100 cc. or less, and then 

 adding this to enough water to make a total of 250 cc. There will then 

 be 10 mg. of the root-inducing substance' in each 2.5 cc. and the quantities 

 of this stock solution which it is necessary to add to each liter of water 

 to make dilute solutions of the following concentrations will be as follows: 

 2.5 cc. for 10 mg./l., 5 cc. for 20 mg./l., 7.5 cc. for 30 mg./l., 10 cc. for 

 40 mg./l., 12.5 cc. for 50 mg./l., 20 cc. for 80 mg./l., and 25 cc. for 100 

 mg./l. Safe and effective concentrations, named below for cuttings of a 

 number of species, depend upon the species, condition of cuttings, and 

 length (in hours) of treatment but this is probably a sufficient range for 

 most species. 



In working with species for which no good treatment is yet known, the 

 propagator, having in mind the concentrations and treatments which are 

 effective with related species, should remember that a treatment which is 

 safe and effective with one species at one time of year mav not be for 

 another species, or even for the same species at other times of year (50). 

 In general, the less mature the wood, the lower should be the concentra- 

 tion or the shorter the treatment (16) although cuttings of some species 

 reach their peak of requirement for concentrations, at least of indolebutyric 

 acid, in October and November (49). 



Low concentrations of indolebutyric acid are effective with herbaceous 



