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Le dCveloppement du bourgeon axillaire du Manihot esclrlenta. Can. J . Bot. 70 : 2041-2052. L'appareil vkgktatif atrien du manioc est constituC de deux sortes d'axes : sylleptiques et proleptiques. Les axillaires, aprks dktermination, peuvent suivre deux types de dtveloppement, soit un dCveloppement anticipt B l'origine des axes sylleptiques, soit un dtveloppement proleptique. Les differences morphologiques entre les deux categories d'axes s'expliquent facilement par les diffkrences d'tvolution des axillaires. Le dtveloppement proleptique s'effectue en quatre ttapes : ( i ) une phase de dttermination, (ii) une phase de latence intramkristematique, (iii) une phase d'organogenkse et (iv) une phase d'inhibition par dominance apicale. Les deuxibme et quatribrne phases n'existent pas dans le dtveloppement anticipt. La phase de latence intramkristematique est due B I'existence d'une double prtstance de l'kbauche foliaire axillante et du point vkgktatif susjacent. L'hypothkse d'un contrble de la determination et de la latence des axillaires depuis le mtristkrne apical caulinaire est discutee. Les contr8les des deux interruptions de dkveloppement, latence intramCristCmatique prtcoce et arrCt tardif par dominance de l'ensemble de l'apex, ne s'exercent pas a la mCrne Cchelle et ne sont vraisemblablement pas de mime nature. Mots clis : bourgeon axillaire, tige, dtveloppement, manioc, pioleptique, sylleptique. MEDARD, R., SELL, Y., and BARNOLA, P. 1992. Le dkveloppement du bourgeon axillaire du Marlihot esc~rlerzta. Can. J. Bot.70: 2041 -2052. The vegetative aerial apparatus of cassava consists of two kinds of axes: sylleptic and proleptic. After its determination, an axillary meristem may have either an advanced development, which characterizes a sylleptic axis, or a later development, which characterizes a proleptic axis. The morphological differences between the two categories of axes are easily explained as the result of differences in development. Proleptic development undergoes four stages: ( i ) determination, (ii) first latent period in the apical meristem, (iii) organogenesis, and (iv) second latency. The second and fourth stages do not occur in the advanced form of development. The first latent stage is due to a double precedency of both the upper part of the apical meristem and the axillary leaf primordium. The hypothesis of a control of the determination and the first latency of the axils from the whole apical meristem is discussed. The regulation of the two types of interruptions of development do not take place on the same scale and are probably not of the same type.

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L' anisocladie, absolument générale, ct l'anisophyllie, très fréquente chez les Acanthacées, révèlent le plus souvent la présence d'un secteur favorisé le long des différents axes d'une plante. Elles donnent naissance à des structures inflorcscentielles unilatérales (J>haulopsis imbricala) qui s'observent également dans de nombreuses inflorescences plus ou moins contractées (.Justicia coma/a, Justicia jurcala, Jacobinia suberecta ct Hypoestes phyllostachya).Zusammenjassung. -J>ic absolut allgcmeinc Anisocladie und die sehr haufige Anisophyllie bei den Acanthaceen lassen mcistcns die Gegcnwart cines gcfôrderlen Sektors entlang der verschiedenen Sprossen einer Pflanze erkcnnen. Sie führen zu unilatcralen Inllores?.ensstmlhau/opsis imbricata), which arc also observeù in many more or less conlracted inflorescences (.Justicia comala, Justicia furcata, Jacobinia suberecta and liypoestes phyl/ostachya). GÉNÉRALITÉS

Analysis of the inflorescence structures of 188 species from French Guyana belonging to the Melastomataceae (Myrtales) confirms that the panicle (of flowers or cymes) is the inflorescence which, under the effect of a homogenization process, gives rise to the determinate raceme (a single raceme of flowers or of cymes, or more rarely, a double raceme), and later by truncation, the indeterminate raceme. The impoverishment of these flowering units can give rise to triads which correspond to uninodal racemes morphologically identical with dichasia (triflorous cymes), albeit of a different origin, since the cyme is considered as resulting from the enrichment of a flower and thus assimilated to the latter as a flowering unit. Extreme impoverishment of these uninodal racemes gives rise to a single flower. Melastomataceae have two peculiar features: successively developing pauciflorous groups and long proliferous shoots with short side shoots specifically for flowering. Within the framework of intrafamily classification, all these inflorescences, by virtue of their great diversity and the series of links between their structural variations, may constitute an essential basis for research on phylogenetic links between taxonomic groups.