Descriptor : general stem pattern (ex-von Mohl's classification)
Descriptor type : categorical
Definition:
Von Mohl (1823–1850) has developed this classification on morphological and anatomical description of some species, which explains that the names of genera are associated with the type definitions. These names are conserved because of their use in previous descriptions. For each type, von Mohl indicated the general pattern of the stem on a radial strip from a transverse section but did not clearly explain how one would choose a category. Thus, it is necessary to delimit these types by numerical intervals of ratios based on: (i) the density (d) of fvb (fvb/cm2); (ii) the f/v ratio, here defined as the average ratio (of about 10 to 30 fvb) between the surface area of f, the fibrous part of a vascular bundle, as seen in transverse section (fibrous dorsal cap, above the phloem and fibrous ventral cap, under the xylem, Fig. 2) and the surface area of v, the vascular part including the paravascular parenchyma (phloem + xylem and paravascular parenchyma, Fig. 2); (iii) the fibrous covering index (R) defined as the ratio between a, the surface area of the fibrous part of all the fvb in an examined transverse section (TS) and A, the whole surface area of the examined TS (R = a/A). In order to define applicable numerical intervals, and because of the high sensitivity of these variables to stem polymorphism, it is necessary to use ratios. These ratios, less sensitive to polymorphism, come from the values of these three variables defined in a radial strip from a transverse section divided in two specific zones of the central cylinder. These zones are the subcortical zone (noted out in subscript) and the central zone (noted in).And the ratios are: d(fvb)out/d(fvb)in; (f/v)out/(f/v)in; (R)out/(R)in.
first publication:
H. v. Mohl. De Palmarum structura. In K. F. v. Martius, éd., Historia naturalis Palmarum. Opus tripartitum, volume 1. Monachii - impensis auctoris ; Lipsiae - apud F. Fleischer, 1823-1850.
english version:
H. v. Mohl. On the structure of the palm-stem. In A. Henfrey, éd., Reports and papers on botany, English translation, pages 1–92. Ray Society, London, 1849.
Comments on these publications:
B. Sahni. Revision of Indian fossil plants: Part iii. Monocotyledons. Monogr. Birbal Sahni Inst. Palaeobot., 1:1–89, 1964.
K. G. Stenzel. Fossile Palmenhölzer. Beitr. Paläontol. Geol. Österr.-Ung. Orient., 16(3-4):107–228, 1904.
von Mohl's classification
Cocos-Type
Cocos-Type
Corypha-Type
Corypha-Type
Mauritia-Type
Mauritia-Type
Calamus-Type
Geonoma-Type
Geonoma-Type
Hierarchy
identification within "subfamily" or "tribe" | |_ general stem pattern (ex-von Mohl's classification) | |_ shape of fibrous part in transverse section {Calamus-Type} | |_ median sinus {Calamus-Type}