. Carnegie Institution of Washington publication. 202 THF MARATTIALES teris is really built up ol leal traces, the so-called "compensating segment" being nothing more than the lower part of ;i leaf trace which higher up emerges as a meshed segment from the outer zone and passes into tbe base of the leaf. The structure of the petiole (fig. 182, .7) is like that ol Marattia, except that the vascular bundles are more numerous and are arranged in several circles, inclos- ing one or two small bundles in tin center. A cross-section ol a leaflet (fig. 182, II) shows the vascular bundle whic
. Carnegie Institution of Washington publication. 202 THF MARATTIALES teris is really built up ol leal traces, the so-called "compensating segment" being nothing more than the lower part of ;i leaf trace which higher up emerges as a meshed segment from the outer zone and passes into tbe base of the leaf. The structure of the petiole (fig. 182, .7) is like that ol Marattia, except that the vascular bundles are more numerous and are arranged in several circles, inclos- ing one or two small bundles in tin center. A cross-section ol a leaflet (fig. 182, II) shows the vascular bundle which traverses the midrib to be horseshoe-shape in section, having a central mass of tracheids, with reticulate or scalariform markings, and surrounded by the phloem, largely made up of large sieve tubes, but having also protophloem cells and bast. The ground tissue is composed largely of paren- chyma, but on both sides below the epidermis is a conspicuous band of collenchyma. In the larger divisions of the leaf the collenchyma, as in Marattia, is replaced by sclerenchyma. The structure of the lamina is very much like that of Dancea, but the palisade parenchyma is even better developed. A comparison was made of the leaves of two forms (species?) of Angiopteris, one from Australia, the other from Ceylon. These showed several notable differ- ences. The leaflets of the Ceylonese specimens were thinner and sharply serrate, /'. t'lo. 182. -Atigiopteris. A. Section of petiole from an adult sporophyte, somewhat reduced. B. Section of a leaflet, col, collenchyma: pt palisade tissue. X14. C. Part of sporophyll, showing the sori. X4. while in the Australian specimens the serrations were almost wanting, except at the tapering apex of the leaflet. There were also marked anatomical differences. In the Australian form the palisade cells are very much elongated and are separated hum the epidermis by a layer of colorless hypodermal cells, and the spongy meso- phyll of the lower part of the leaf i
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Keywords: ., bookauthorcarnegie, bookcentury1900, bookdecade1910, bookyear1911
