The occurrence of vertical resin canals in Keteleeria, with reference to its systematic position in Pinaceae

The variation in the number of resin canals in the secondary xylem of Keteleeria fortunei (A. Murray bis) Carrière is determined. At all levels from base to top of a tree, resin canals are absent rearer the pith, but they (sporadically) appear after a certain cambial age. In addition, the occurrence of resin canals in seven named species of Keteleeria was surveyed. It was confirmed that normal vertical resin canals do occur in the mature parts of secondary xylem, but that they may be absent in the juvenile parts of secondary xylem of stems, as well as in branches and in seedlings or saplings. Earlier investigations reporting the absence of resin canals altogether in this genus may have been misled by the use of younger (immature) specimens instead of mature stems of trees. The distribution pattern of resin canals found in Keteleeria is systematically significant because it supports a new system of classification of Pinaceae, in which Keteleeria is believed to have a close relationship with Nothotsuga.     

Biodiversity of Pinus (Pinaceae) in Mexico: speciation and palaeo-endemism

Mexico, with 43 species of Pinus recognized in the most recent revision for Flora Neotropica, is the richest centre of diversity for the genus. Other centres are California and south-east U.S.A. In comparison, Eurasian pine regions are less diverse. This biogeography, combined with the virtual absence of fossil evidence in Mexico, has led to the consensus that Pinus is a relative newcomer to the region and that 'recent' speciation accounts for its diversity. Phylogenetic analysis indicates that several of the oldest and most primitive members of the genus may have originated in this part of the continent and coexist with the species resulting from more recent radiation.     

Pilgerodendron uviferum（柏科）及其相关类群叶角质层微形态特征的比较研究

在扫描电镜下观察了分布于南半球的柏科Cupressaceae单种属Pilgerodendron u viferum及其相关类群的代表种Austrocedrus chilensis、Libocedrus plumosa和Papuacedr us papuana叶角质层内外表面的微形态特征。发现Pilgerodendron uviferum叶角质层外表面 光滑,不具Florin环,而其余3个属的代表种均有明显的Florin环;且仅L.plumosa叶角质层外 表面有乳状突起。观察结果支持传统的观点,即将P.uviferum作为独立的属;不支持基于DNA 分析的结果,即将P.uviferum归并到Libocedrus属。发现Papuacedrus papuana叶角质层外表 面有许多明显的小凹陷,与其相对应的叶角质层内表面有凹陷的小狭缝,该性状以前未见报 道。     

Cone and ovule development in Cunninghamia and Taiwania (Cupressaceae sensu lato) and its significance for conifer evolution

We examined the early developmental stages of the seed cones and seeds of two conifer genera, Cunninghamia and Taiwania, using scanning electron microscope (SEM) images of freshly collected material. In recent similar studies, these two taxa were not described. The present paper aims to fill that gap. Both genera appear to have features crucial to the understanding of the evolution of the cupressaceous cone, characteristic of the families Cupressaceae and Taxodiaceae, and provide further evidence for the need to merge these families. These features are: the ovuliferous scale in Cunninghamia develops as a small lobe with each of three ovules; in Taiwania these lobes are absent, but a small ridge could be a vestige of them. In neither of these two genera does an ovuliferous scale develop to maturity and only limited intercalary growth transforms the bracts, of which only their width and final shape distinguishes them from sterile leaves. Thus, the bracts, not the ovuliferous scales, form the mature cone in these two genera. This trend is continued in more derived genera of Cupressaceae. Another key extant taxon that has helped to elucidate the evolution of this type of conifer cone is Sciadopitys; similar studies have already been done on this genus, and we compared our findings to them. We also considered certain fossil Mesozoic conifer cones, which shed further light on the evolution of the cupressaceous cone. The evidence from these various genera strongly indicates that recently reconstructed phylogenies of gymnosperms based on molecular evidence from extant taxa do not reflect the evolution that actually happened. Such studies need to take into account nonmolecular evidence, as detailed here.