中国古生代两种种子的研究

STUDIES ON TWO PALAEOZOIC SEEDS FROM CHINA

本文报道发现于我国山西和贵州两省的煤核中两种种子:小心籽(订正)[Cardiocarpusminor(Wang)emend]和双籽(未定种)(Diplotesta sp.),并对这两种种子进行了描述,讨论了它们的分类位置。作者认为小心籽的珠心维管束的分布不同于该属的其他种,而这又是两侧对称种子分类的一个重要依据,因此,建议把它保留于心籽属中,并对它的种的特征进行了订正。

This paper reports two species of the seed order Cardiocarpales:Cardiocarpus minor (Wang) emend and Diplotesta sp.which were found in coal balls.The specimens were collected from Taiyan Formation of Upper Carboniferous near Xiedao Village,West Mountain, Taiyan City,Shanxi Province and Wangjiazhai Formation of Upper Permian of Wangjiazhai Mine of Shuicheng district,Guizhou Province,China. The two taxa are described and their taxonomy is discussed in detail.The diagnosis of the species (Cardiocarpus minor (Wang) emend) is amended as follows: Seeds bilaterally symmetric and thinner cardioformed,appoximatly 4-6 mm long,3-4 mm wide in the primary section and less than 2 mm thick in the secondary section.Integument differentiated into three zones.Outer sarcotesta delimitted into four layers:1) carbonized cuticle partly preserved;2) epidermis of thin-walled parenchyma 1-2 rows of small cells;3) hypodermis of secretory tissue containing large cells,uniform in thickness;and 4) parenchyma layer consisting of thin-walled cells in size varying from 20 to 50 μm middle sclerotesta of vertically arranged fibers is bipartite:outer fibers being smaller in diameter and possess- ing thicker walls than inner fibers.Sclerotesta 80 μm in thickness commissural laterally to form two lateral ribs. Inner endotesta single rowed of parenchymatous cells.Nucellus free except at base which is attached to the integument by narrow nucellar platform.Pollen chamber not observed. The double vascular system includes integumentary strand beneath secretory layer of sarcotesta and nucellar strand which forms a tracheid mentle;the origin of integumentry and nucellar strands unknown. In addition a computerized three-dimensional reconstuction techniqne is utilized to reconstruct membrane like structure of Diplotesta sp.It is suggested that Cardiocarpus minor is different from other species of the genus Cardiocarpus in the distribution of nucellar vascular tissues.This feature is thonght to be one of the important characters of bilaterally symmetrical seeds in a taxonomic view point.Therefore Cardiocarpus minor wang probally represents a menber of another new seed genus,althongh this species remains in the genus Cardiocarpus.