On the multiperforate plates occurring in the xylem vessels of some monocotyledonous roots

Abstract

The occurrence and structure of multiperforate plates in the xylem vessels of the roots of some monocotyledons are described. Such plates are present in all the vessel segments of the roots of many members of the family Araceae and inCrinum asiaticum. In all these plants vessel segments with simple perforations have not been observed. The vessel segments as found in these roots may be of three types : (i) those having oblique end walls at both ends; (ii) those having oblique end wall at one end and transverse or slightly inclined end wall at the other; (iii) those having transverse or slightly inclined end wall at both ends. The perforation plates of these segments may be scalariform, scalariform with branched bars, or reticulate. The bars of the plates can be correlated to the scalariform-reticulate thickening of the lateral walls of the vessel segments. These types of vessel segments are regarded as forming a primitive feature. Further it is concluded that the xylem vessels of roots have developed phylogenetically from typical scalariform tracheids by the loss of pit membranes at their ends.