Exomorphology and internal structure of cypselas of seven species of the tribe cardueae (compositae)

Cypselar morpho-anatomy is very helpful for the separation of taxa, when flowering condition is unavailable i.e. fruiting condition is available. For this purpose, cypselas of seven species belonging to five genera (Arctium lappa, Cirsium arvense, Cirsium candelabrum, Cirsium heleniodes, Mantisalca salmantica, Saussurea fastuosa and Xeranthemum annuum) of the tribe Cardueae have been investigated. The important morphological features are the presence of surface structure, pappus bristles, stylopodia, carpopodia with cellular orientation etc. Except in the cypselas of Mantisalca salmantica and Arctium lappa, the remaining 5 studied cypselas are homomorphic. In the cypsela of Xeranthemum annuum, surface is pubescent, whereas in remaining 6 studied cypselas, surface is rough and glabrous. In the cypsela of Arctium lappa, Cirsium arvense, Cirsium heleniodes and Cirsium candelabrum, stylopodia are prominent and enlarge than the remaining studied cypselas where they are inconspicuous. Carpopodia are the basal, meristematic zone of cypselas. In the cypsela of Cirsium arvense, Arctium lappa, Mantisalca salmantica and Cirsium candelabrum, pseudocarpopodia are present, whereas in remaining studied cypselas carpopodial cells are arranged from 1 layer (Cirsium heleniodes, Xeranthemum annuum) to 2 layers (Saussurea fastuosa). Pappus structures help in the dispersal of cypselas. In the cypsela of Saussurea fastuosa, Cirsium heleniodes and Cirsium candelabrum, plumose type of pappus bristles are present, whereas in the cypsela of Mantisalca salmantica barbellate pappus bristles are present. In the cypsela of Xeranthemum annum, scaly pappus is present. Among the studied cypselas, in Arctium lappa and Cirsium arvense, pappus are absent. Anatomically, the mesocarpic region is very interesting than other layer of pericarp. In the cypsela of Saussurea fastuosa, Cirsium heleniodes and Xeranthemum annuum, mesocarpic regions are heterogeneously developed than the other studied cypselas where mesocarpic regions are homogenously developed. In the cypsela of Arctium lappa, crystal is present in the mesocarpic region but in six studied cypselas crystals are absent. Presence of secretary duct is also an important taxonomic character and which is present in the mesocarpic region of the cypsela of Mantisalca salmantica and Cirsium candelabrum. In remaining five studied cypselas, secretary ducts are absent. In the cypsela of Cirsium candelabrum, internal to the testal region vellicular cavity is present, whereas in the cypsela of Xeranthemum annuum, vellicular cavity is present within the mesocarpic region. In the cypsela of Saussurea fastuosa and Xeranthemum annuum, testal layers are made up of round-elongated, uni-seriately arranged, parenchyma cells, whereas in rest studied cypselas, testal layers are made up of vertically arranged, thick-walled, palisade parenchyma cells.