Resumo em Inglês:

1) The present paper deals with variations in the structure of the inflorescences of the Maydeae Americanae, especially of the ear of Zea Mays, which came under observation during our genetical studies during the last 10 years. Care was tauken to include only such structures which were observed frequently and had in general an aspect which could not be described as a pathological abnormality, but rather as a reversion to a phylogenetically primitive type or as a new form. The aberrations may be summarized as follows: a) Individual flowers. Eeversion to the hermaphrodite state of the usually unisexual flowers in Maydeae were described. Such flowers are however already so well known that no details need to be given. b) Many flowered spikelets. The spikelet in all the American Maydeae are normally two flowered. In forms of tunicata, obtained by selection, spikelets were obtained with up to three perfect flowers, all producing well developed kernels (Fig. 4-6), with a maximum of five flowers. The structure of three-flowered spikelets is explained in the diagrams Fig. 2 and 3. Owing to the organization of the flowers, the embryos of the first and third are turned towards the base of the inflorescence and the embryo of the second flower towards its tip. The embryos in two-flowered epike-lets are normally turned to the base (first flower) and to the tip (second flower). (Cutler, 10). Cases were observed of three flowered spikelets with one abortive flower, both the remaining embryos, produced by the first and third flower, turned towards the base of the inflorescence. c) Number of spikelets per alveolus. In maize and in the male parts of the inflorescences of Euchlaena and Tripsacum two spikelets are formed per alveolus, while in the female parts of the latter genera one spikelet is present, though occasionally exceptions are found. Collins (8) explained the appearance of the double spikelet as remainder of a small spikelet branch which has been lost during evolution. The normal structure and that of a spikelet branch is shown schematically in Fig. 3, e-f. In the tassels of several tunicata plants small and regular branches of spikelets appeared in the alveoli, their fo