臺灣一葉蘭之觀察

Observations on Pleione formosana Hayata

This report is a continuation of my studies on Pleione formosana Hayata and deals with the internal structure and differentiation of the roots, pigmentation, variation and differentiation of unfertilized flowers (Chen, 1968). The primordia of adventitious roots are hidden in the unbroken buds, with numbers ranging from several (3 or 4) to thirty. In the transection of the mature root, there are two to several layers of velamen whose cytoplasm and nucleus disappears from the cell that enclose the cylinder. They are strongly lignified and easily shed. The exodermis takes the place of the function of velamen after the latter dies. Cortical cells are nearly circular and isodiametric. Beneath the endoderm, there are 2 to 3 layers of thick-walled cells surrounding the vascular bundle. The pericycle is absent. The central pith is concealed by radiate vascular tissue. In the longisection of the root, all the tissues originate from one group of initials, i. e. root cap, velamen, cortex and vascular cylinder are all differentiated from one group of cells. The flowers of Pleione are dioecious and epigynous. They contain a 3-carpeled ovary and an anther with floral appendages. During the blooming period, cross-pollination occurs. After pollination both the pollen and the nucellus ripen. In the apical meristem a second flower remains undeveloped. The natural occurrence of a second and a third flower on one scape is an evidence of its tendency to form a spike. By analyzing the pigments in purple flowers it is found that there are four pigment groups, i. e., anthocyanins, flavones, flavonols and aurones. But in white flowers only flavones and aurones are found. The result on the paper chromatogram shows that six kinds of anthocyanins are found in flowers and these are different from those in pseudobulbs. The maximum absorption of the anthocyanin extract is at 520 mµ. The abscission of the leaf is almost the same as that of the pedicel. The nuclei disappear and cell walls do not stain with safranin in the cells beyond the abscission layer, but the cells connected with the plant body are lignified and stain red with safranin.