SOME OBSERVATIONS ON THE GIRDLE OF ACHNANTHES LONGIPES

Abstract

The girdle of Achnanthes longipes has been studied using scanning and transmission electron microscopy. An examination of 132 isolated bands showed that they can be classified into 3 main morphological types, all of which are usually open at one end, and bear poroids with occlusions recalling those of the valve poroids. The most advalvar band (band 1 or valvocopula) has a single row of elongated poroids on the pars exterior. The poroids have a groove-like appearance in internal views. The band interlocks with the valve following the complementary shape of its pars interior and the internal valve margin. Type 2 bands, which follow the valvocopula in the abvalvar direction, have a ligula or ligula-like expansion at the closed end, with no antiligula; their pars exterior usually bears 2 rows of circular poroids. A type 2 band seems to interlock with the valvocopula via its crenulate pars interior. The crenations may interact internally with the poroids of the valvocopula, or the cavities marking the limit between pars interior and pars exterior of the valvocopula. Presumably, type 2 bands also interlock with other type 2 bands. Type 3 bands follow type 2 bands in the abvalvar direction. They differ from type 2 bands especially in the smooth pars interior, which probably makes the interlock with type 2 bands looser than between type 2 and 1 bands, or between band 1 and the valve. Mature cingula have a total of 6 bands each. In addition to the single type 1 band, there are probably four type 2 bands and one type 3 band.