Archive image from page 71 of The developmental anatomy of Isoetes. The developmental anatomy of Isoetes . developmentalana31paol Year: 1963 58 THE DEVELOPMENTAL ANATOMY OF IsoeteS Prthostichies Basal Furrow, or Groove Fig. 14. Sketch of the lower surface of a mature sporophyte in which the Hving roots were limited to one row along each side of the basal furrow. These two rows each form a series of roots. The members of the two series are on alternate orthostichies. Schematic. The abbreviation 'orth.' is used for 'orthos- tichy' in figures 15 to 19. series occupy alternate orthostichies. T
Archive image from page 71 of The developmental anatomy of Isoetes. The developmental anatomy of Isoetes . developmentalana31paol Year: 1963 58 THE DEVELOPMENTAL ANATOMY OF IsoeteS Prthostichies Basal Furrow, or Groove Fig. 14. Sketch of the lower surface of a mature sporophyte in which the Hving roots were limited to one row along each side of the basal furrow. These two rows each form a series of roots. The members of the two series are on alternate orthostichies. Schematic. The abbreviation 'orth.' is used for 'orthos- tichy' in figures 15 to 19. series occupy alternate orthostichies. This alternation can be seen in plate 16, B, by comparing series S and S'. A precise designation of the location of roots or root traces is obtained when the locations are represented graphically. For this purpose, it is best to view transverse sections of two-lobed specimens in a standard- ized position so that the basal furrow runs from left to right. A drawing of the section may then be related to a set of coordinates by the follow- ing procedure. A straight line is drawn through the middle of the furrow and is regarded as the x-axis. Series of roots lie more or less parallel to the X-axis. The perpendicular bisector of the x-axis is drawn and is named the y-axis. Orthostichies appear in cross-sections along lines which are more or less parallel to the y-axis. In some plants the y-axis contains an orthostichy. Such an orthostichy is the zero orthostichy (0-orthostichy), which is the most basal in the plant. Orthostichies located to the right of the y-axis receive values that are consecutive and increasingly posi-
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