Apical sections of resting potato tuber.s of the varietj' Majestic, -whicb is for a loug rest-period, -were treated for 6 and 24 bours -with water or witb the cytokiuius kinetiu or zeatiu. The cytokiuiu-treatment breaks the rest-period very rapidty. Ttie buds begiu to sprout already after 2-3 days. The content of acid inhibitors (the (} inhibitor) iu extracts of the peelings from cytokiuiu-treated sections is much lower than iu similar extracts froui water-treated, resting sections. Alreadv 6 hours after the beginning of tbe treatment, differences iu iubibitor content can be demonstrated.

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Different types of plant material, including both dry and swollen maize kernels, swollen bean seeds, bean seedlings and dry rose seeds, were extracted by different methods and the yield of IAA was determined with the indolo‐α‐pyrone method. Extraction of dry maize kernels during short time experiments, varying from 3 to 24 h, gave the highest IAA yield when methanol was the extractant and a significant lower yield when diethyl ether or dichloromethane were used. The duration of the extraction period increased the yield with all the extractants. Progressive extractions for several days or weeks had little effect on the yield when 100% acetone was used in contrast to methanol and ether as extractants, which increased the yield during prolonged extraction. Extractions of tissue treated to 100°C for 1 h contradicted the hypothesis that IAA is enzymatically liberated during ether extraction. Water in the extractant solvents increased the yields. This was most pronounced when aqueous acetone was used instead of 100% acetone. Increased extraction temperature augmented the IAA yields. The yield of IAA from other types of tissue extracted with methanol for periods of 3 or 24 h was, however, independent of the duration of the extraction time. This indicates that some tissues contain less not easily extractable IAA than dry maize kernels. The terms “free” and “bound” IAA are discussed; they should be replaced by “easily extractable” and “not easily extractable” IAA. The results also show that IPyA in vitro can partly be converted to IAA during extraction and fractionation.