Аннотация:Completely ascidiate carpels (often with funnel-shaped stigmas)are especially common among tepaloid alismatids (basal monocot order Alismatales). Along all their length, these carpels represent
a tubular structure with ventrally attached single pendent ovule. There is a considerable piece of tissue between ovule and carpel margin. Developmentally, the ovule originates on the ventral placenta
which is located in the cross-zone. Usually, ovule initiation happens early in the development when the carpel is represented by low meristematic rim. As the carpel walls grow, the ovule attachment becomes lifted above the receptacle. Thus, the ovary is formed by circular zonal growth below the level of placenta.The most intriguing process is style development which proceeds via circular growth above the level of placenta. We speculate that directly above the cross-zone a new, secondary carpel margin appears. The cross-zone itself is a marginal meristem to build up the ventral carpel wall and to produce the ovule. Technically, the cross-zone becomes exhausted by ovule initiation and the growth of carpel wall ceases ventrally after ovule initiation in many angiosperms.To continue with tubular style, a new meristematic activity is needed above the ovule. The secondary ventral carpel
margin as a result of such an activity develops more slowly than lateral flanks. This leads to slit appearance of carpel orifice which faces ventrally. During further development, the carpel orifice
becomes more or less horizontal. The work was performed with funding from the Russian Science oundation (project 14-14-00250).