species, however, were M = 0.46D46 (r2 = 0.99, N = 41), M = 0.07D32 (r2 = 0.91, N = 65), M = 0.56D22 (r2 = 0.92, N = 85), and M = 0.44D1 8 (r2 = 0.97, N = 21), respectively, indicating that the proportionality M oc D--30 recedes with finer taxonomic resolution. The data for Cooksonia were found to comply with the allometry of Polytrichum when the regression curve of this moss was extrapolated into the size range of the fossil species. Analyses showed that intraspecific allometric scaling factors a were dependent upon the manner in which plant stems taper. Species or portions of branching systems with a > 4.0 had essentially untapered stems (e.g., Polytrichum commune, Psilotum nudum, twigs of Larix decidua); species with a < 2.2 had tapered stems resulting from secondary growth in most cases. The evolution of tapered primary stems and secondary growth was interpreted to alter reproductive allometry. This paper provides intra- and interspecific allometric descriptions of the relation between reproductive biomass and stem diameter for a total of 12 extant moss, pteridophyte, and gymnosperm species. Comparable descriptions are provided for the fossil remains of the early Paleozoic vascular plant remains of the rhyniophyte Cooksonia pertoni and the trimerophyte Psilophyton princeps. Quantitative descriptions of the relation between biomass and plant size provide useful rules to estimate the allocation of resources to reproductive, mechanical, and other functions. General allometric relations for this purpose are available for species of angiosperm trees (Murray, 1927; Whittaker and Woodwell, 1968; Mc
[1]
T. McMahon,et al.
Size and Shape in Biology
,
1973,
Science.
[2]
C. D. Murray.
A RELATIONSHIP BETWEEN CIRCUMFERENCE AND WEIGHT IN TREES AND ITS BEARING ON BRANCHING ANGLES
,
1927,
The Journal of general physiology.
[3]
P. White.
Corner's Rules in Eastern Deciduous Trees: Allometry and Its Implications for the Adaptive Architecture of Trees
,
1983
.
[4]
G. M. Woodwell,et al.
DIMENSION AND PRODUCTION RELATIONS OF TREES AND SHRUBS IN THE BROOKHAVEN FOREST, NEW YORK.
,
1968
.
[5]
F. James Rohlf,et al.
Biometry: The Principles and Practice of Statistics in Biological Research
,
1969
.
[6]
L. Axe,et al.
A vascular conducting strand in the early land plant Cooksonia
,
1992,
Nature.
[7]
T. McMahon.
The Mechanical Design of Trees
,
1975
.
[8]
Karl J. Niklas,et al.
Plant Biomechanics: An Engineering Approach to Plant Form and Function
,
1993
.
[9]
R. M. Lanner.
Adaptations of whitebark pine for seed dispersal by Clark's Nutcracker
,
1982
.