The presence, in plants extracts, of factors capable of promoting cell division has been known for some time (Goldacre and Bottomley 1959;Miller 1961) and such compounds have been partially purified (Miller 1961; Zwar, Bottomley, and Kelford 1963). The germination of seeds normally involves cell division as well as cell enlargement (Mayer and Poljakolf-Mayber 1963). Therefore it seemed of interest to investigate whether kinins occur in seeds or are formed during their germination. Lettuce seeds were used because their physiology has been studied extensively. We have also tried to partially characterize their kinins. MethodsKinin activity was assayed biologically. The test objects were disks of stem pith from tobacco, Nicotiana tabacum cv. Seratina. The pith was removed from externally sterilized stem sections, taken 20 em from the stem apex. The disks, 2-3 mm in diameter and 2-3 mm thick, were obtained aseptically and were prepared fresh for each experiment. They were floated in petri dishes on culture medium prior to sowiug into erlenmeyer flasks containing 20 ml of medium solidified with agar. The medium was that of Zwar and Skoog (1963), but with their concentrations of inorganic nutrients doubled.Two controls were used: in both 0·2 p.p.m. 3-indolylacetic acid (IAA) was added to the basal medium and in one 0·2p.p.m. of kinetin was also added. In those containing 0·2 p.p.m. kinetin normally 9 out of 10 sections grew, while in those without kinetin growth was absent. When extracts were tested they were substituted for the kinetin. The flasks were kept in the dark at 26'0 and covered with polythene in order to reduce drying out of the culture. IGnin activity was assayed visually by determining whether the pith had undergone cell division after 2-4 weeks Zwar, Bottomley, and Kelford 1963;Zwar and Skoog 1963). Oen division could be easily detected visually and was confirmed by microscopic examination of cells from the disks. Kinin activity is expressed as the number of disks showing cell division in a given number of replicates as compared to controls without kinin.Lots of 1 g of lettuce seeds, cv. Grand Rapids, were germinated in petri dishes with 3 ml water and given a light stimulus of 30 sec exposure to red light after imbibition for I hr, and then placed in the dark at 26'0 (EvenariandNeumann 1953). Mter 48 hr germination was 100%. >I< Manuscript