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Our knowledf^e of auxiu in trees is very limited. Czaja (4) found Ibal auxin occurs iu shooting,' buds of some deciduous free .species and oi Pinu.s siluestris, Pinus Hcdreichii and Picca f)un(jens. Czaja made his examinations in such a uay that he cut suitably small pieces from the huds and then placed them on one side of dec:i]>itated .\veiia enleoptiles. Ziminermann ilO) investif^ated the quantity t)f auxin iu huds of I'inus strohu.^ aud IHccd excelsa. He placed the buds on plates of ai,'ar into which auxin diffused. The agar was then tested ou coleoptiles. Zimmermaim found thai Ihe termiiud hud of the main stem docs not contain any auxin during the winter. When the huds hegin to develop they are, however, rich in auxin and the correspoiidinft erminal huds of laleral shoots contain auxin in ([uantities which decrease with increasing age (tf the whorls. .Avery. Burkholder and Creighton (1) examined Aesculus and found that Ihe presence of auxin in older slenis is prohahly connected with the activity of the cambium. Mirov (0) fouud iu /^(/j(/.v fiondcrosa that In fast-growing trees there is no difference in quantity of auxin hetween terminal and lateral huds. Such a difference is. on the other hand, tbund in slow-growing trees, in which there is more auxin in terminal than iu lateral huds.Thus it is proved that auxins exist iu hoth deciduous and coniferous trees. However, it has not a.s yet l>een ascertained if these auxins are identical wilh any of the native auxins already known. The i)urpose of the present work has been lo study Ihc jiuxiii Ihat is fouud in younger parts of the stem of Pinus silvt'slris and cnuipare it wilh [^ indolyhu-etic acid. The suhstance or the substances in the ])ines thai arc resjjonsihle for Ihe auxin activity lound are in this paper called pine auxin.[544]

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